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Rifampicin is a frontline antibiotic in the management of tuberculosis. Since no spectrofluorimetric methods are reported for this drug, this approach was challenged to craft a sensitive, reliable, valid, fast, and green methodology. In recent years, fluorescence spectroscopy has received a lot of interest. Its benefits include ecological greenness and analytical performance. The pharmaceutical industries greatly like this approach because of its low energy and decreased solvent usage, which make it both economical and environmentally friendly. This methodology was based on utilizing the enhanced native fluorescence of the rifampicin at 341 nm after excitation at 241 nm in a beta-cyclodextrin micellar system. Modern developments in analytical chemistry have been applied to reduce risks to the workplace and environment by using distilled water as a dilution solvent for method application and optimization. The method was found excellent green with 97 eco-scale and 0.86 AGREE scores besides an 89.6 overall whiteness score. The range of linearity for rifampicin raw material was 0.2-1.5 μg·mL -1 , and the average recoveries for raw material and spiked plasma were 100.15% and 99.64%, respectively. The suggested technique worked well for the commercial oral syrup of Rimactane® and did not conflict with any common additives., (© 2024 John Wiley & Sons Ltd.)

4 β -Hydroxycholesterol (4 β -HC) in plasma has been used as a biomarker to assess CYP3A drug-drug interaction (DDI) potential during drug development. However, due to the long half-life and narrow dynamic range of 4 β -HC, its use has been limited to the identification of CYP3A inducers, but not CYP3A inhibitors. The formation of 1 β -hydroxydeoxycholic acid (1 β -OH DCA) from deoxycholic acid (DCA) is mediated by CYP3A, thus 1 β -OH DCA can potentially serve as an alternative to 4 β -HC for assessment of CYP3A DDI potential. To study this feasibility, we developed a sensitive liquid chromatography-tandem mass spectrometry method for the simultaneous quantitation of 1 β -OH DCA and its glycine and taurine conjugates in human plasma with the lower limit of quantitation of 50 pg/ml, which enabled the quantitation of basal levels and further reduction. The method was applied to a DDI study to assess how 1 β -OH DCA and its glycine and taurine conjugates would respond to CYP3A induction or inhibition. Rifampin induction resulted in an increase of 1 β -OH DCA and its conjugates in plasma, with 6.8-, 7.8-, 8.3-, and 10.3-fold increases of area under the curve from the time of dosing to the last measurable concentration (AUC LST ), area under the curve from the time of dosing to 24 hours (AUC 24h ), C max , and mean concentrations for total 1 β -OH DCA (total of all three forms), respectively. Importantly, inhibition with itraconazole resulted in notable reduction of these biomarkers, with 84%, 85%, 82%, and 81% reductions of AUC LST , AUC 24h , C max , and mean concentrations for total 1 β -OH DCA, respectively. These preliminary data demonstrate for the first time that total 1 β -OH DCA in plasma has the potential to serve as a biomarker for CYP3A DDI assessment in early clinical development and may provide key advantages over 4 β -HC. SIGNIFICANCE STATEMENT: The authors have reported the use of total 1 β -hydroxydeoxycholic acid (1 β -OH DCA) (sum of 1 β -OH DCA and its glycine and taurine conjugates) plasma exposure as a biomarker for CYP3A activity. Itraconazole inhibition led to an 81%-85% decrease of total 1 β -OH DCA plasma exposures, whereas rifampin induction led to a 6.8- to 10.3-fold increase of total 1 β -OH DCA plasma exposures. Using 1 β -OH DCA exposures in plasma also provides the benefit of allowing pharmacokinetic and biomarker assessment using the same matrix., (Copyright © 2024 by The American Society for Pharmacology and Experimental Therapeutics.)

A fluorescent sensing material based on the ternary core-shell quantum dots with outstanding optical properties and a bio-inspired molecularly imprinted polymer (MIP) as a recognition element has been prepared for selective detection of rifampicin (RFP). Firstly, AgInS 2 /ZnS core/shell quantum dots (ZAIS QDs) were prepared by a hydrothermal process. Then, the fluorescent sensor was prepared by coating these QDs by a dopamine-based MIP layer. The fluorescence of MIP@ZAIS QDs was quenched by RFP probably due to the photoinduced electron transfer process. The quenching constant was much higher for MIP@ZAIS QDs than the non-imprinted polymer@QDs, indicating that MIP@ZAIS QDs could selectively recognize RFP. Under the optimized conditions, the sensor had a good linear relationship at the RFP concentration range of 5.0 to 300 nM and the limit of detection was 1.25 nM. The respond time of the MIP@ZAIS QDs was 5 min, and the imprinting factor was 6.3. It also showed good recoveries ranging from 98 to 101%, for analysis of human plasma samples. The method is simple and effective for the detection of RFP and offers a practical application for the rapid analysis of human plasma samples., (© 2024. The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry.)

Objective: To assess the pharmacokinetics and safety/tolerability of isoniazid, rifampicin and pyrazinamide in children and adolescents with tuberculous meningitis (TBM)., Design: Prospective observational pharmacokinetic study with an exploratory pharmacokinetic/pharmacodynamic analysis., Setting: Hasan Sadikin Hospital, Bandung, Indonesia., Patients: Individuals aged 0-18 years clinically diagnosed with TBM and receiving first-line anti-tuberculosis drug dosages according to revised WHO-recommended treatment guidelines., Interventions: Plasma and cerebrospinal fluid (CSF) concentrations of isoniazid, rifampicin and pyrazinamide were assessed on days 2 and 10 of treatment., Main Outcome Measures: Plasma exposures during the daily dosing interval (AUC 0-24 ), peak plasma concentrations ( C max ) and CSF concentrations., Results: Among 20 eligible patients, geometric mean AUC 0-24 of isoniazid, rifampicin and pyrazinamide was 18.5, 66.9 and 315.5 hour∙mg/L on day 2; and 14.5, 71.8 and 328.4 hour∙mg/L on day 10, respectively. Large interindividual variabilities were observed in AUC 0-24 and C max of all drugs. All patients had suboptimal rifampicin AUC 0-24 for TBM treatment indication and very low rifampicin CSF concentrations. Four patients developed grade 2-3 drug-induced liver injury (DILI) within the first 4 weeks of treatment, in whom anti-tuberculosis drugs were temporarily stopped, and no DILI recurred after reintroduction of rifampicin and isoniazid. AUC 0-24 of isoniazid, rifampicin and pyrazinamide along with C max of isoniazid and pyrazinamide on day 10 were higher in patients who developed DILI than those without DILI (p<0.05)., Conclusion: Higher rifampicin doses are strongly warranted in treatment of children and adolescents with TBM. The association between higher plasma concentrations of isoniazid, rifampicin and pyrazinamide and the development of DILI needs confirmatory studies., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY. Published by BMJ.)

Background and Objective: Increased glycine availability at the synaptic cleft may enhance N-methyl-D-aspartate receptor signalling and provide a promising therapeutic strategy for cognitive impairment associated with schizophrenia. These studies aimed to assess the pharmacokinetics of BI 425809, a potent glycine-transporter-1 inhibitor, when co-administered with a strong cytochrome P450 3A4 (CYP3A4) inhibitor (itraconazole) and inducer (rifampicin)., Methods: In vitro studies using recombinant CYPs, human liver microsomes, and human hepatocytes were conducted to determine the CYP isoforms responsible for BI 425809 metabolism. In addition, two open-label, fixed-treatment period, phase I studies in healthy male volunteers are described. Period 1: participants received oral BI 425809 25 mg (single dose) on day 1; period 2: participants received multiple doses, across 10 days, of oral itraconazole or rifampicin combined with a single dose of oral BI 425809 25 mg on day 4/7 of the itraconazole/rifampicin treatment, respectively. Pharmacokinetic and safety endpoints were assessed in the absence/presence of itraconazole/rifampicin and included area under the concentration-time curve (AUC) over the time interval 0-167 h (AUC 0‒167 ; itraconazole), 0-168 h (AUC 0‒168 ; rifampicin), or 0-infinity (AUC 0-∞ ; rifampicin and itraconazole), maximum measured concentration (C max ) of BI 425809, and adverse events., Results: In vitro results suggested that CYP3A4 accounted for ≥ 90% of the metabolism of BI 425809. BI 425809 exposure (adjusted geometric mean ratio [%]) was higher in the presence of itraconazole (AUC 0‒167 : 265.3; AUC 0-∞ : 597.0; C max : 116.1) and lower in the presence of rifampicin (AUC 0‒168 : 10.3; AUC 0-∞ : 9.8; C max : 37.4) compared with BI 425809 alone. Investigational treatments were well tolerated., Conclusions: Systemic exposure of BI 425809 was altered in the presence of strong CYP3A4 modulators, corroborating in vitro results that CYP3A4 mediates a major metabolic pathway for BI 425809., Trial Registration Number: NCT02342717 (registered on 15 January 2015) and NCT03082183 (registered on 10 March 2017)., (© 2021. The Author(s).)

The pharmacokinetic profiling of drug substances and corresponding metabolites in the biological matrix is one of the most informative tools for the treatment efficacy assessment. Therefore, to satisfy the need for comprehensive monitoring of anti-tuberculosis drugs in human plasma, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous quantification of first-line anti-tuberculosis drugs (ethambutol, isoniazid, pyrazinamide, and rifampicin) along with their six primary metabolites. Simple single-step protein precipitation with methanol was chosen as the most convenient sample pre-treatment method. Chromatographic separation of the ten analyte mixture was achieved within 10 minutes on a reverse-phase C8 column using mobile phase gradient mode. The multiple reaction monitoring mode (MRM) was used for analyte detection and quantification in patient samples. The chosen quantification ranges fully covered expected plasma concentrations. The method exhibited acceptable selectivity; the within- and between-run accuracy ranged from 87.2 to 113.6%, but within- and between-run precision was between 1.6 and 14.9% (at the LLOQ level CV < 20%). Although the response of the isonicotinic acid varied depending on the matrix source (CV 21.8%), validation results proved that such inconsistency does not affect the accuracy and precision of results. If stored at room temperature plasma samples should be processed within 4 h after collection, temporary storage at -20 °C up to 24 h is acceptable due to stability issues of analytes. The developed method was applied for the patient sample analysis (n = 34) receiving anti-tuberculosis treatment with the first-line drugs., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The aim of this study was to establish and validate an alternative high-performance liquid chromatography method for simultaneous quantification of pyrazinamide, isoniazid, acetyl-isoniazid and rifampicin in plasma of patients under treatment for tuberculosis. The performed method was lineal (r 2  > 0.99) in the range of 2.00-50.00 μg/mL for pyrazinamide, 0.50-20.00 μg/mL for both acetyl-isoniazid and isoniazid, and 1.20-25.00 μg/mL for rifampicin. Precision and trueness were demonstrated with coefficient of variation < 15% and deviations < 15%, respectively, for quality controls samples. The lower limits of quantification were 2.00, 0.50, 0.50, and 1.20 μg/mL for pyrazinamide, isoniazid, acetyl-isoniazid and rifampicin, respectively. The method was applied for the analysis of plasma from patients with tuberculosis. This method allowed ensuring reliable quantification of the target compounds and their pharmacokinetics parameters. In general, the mean values of maximum concentration of each antituberculosis drug were located within their respective reference therapeutic ranges. However, patients with sub-therapeutic plasma concentrations of isoniazid and rifampicin were detected. This is the first analytical technique that simultaneously quantifies isoniazid, acetyl-isoniazid, rifampicin, and pyrazinamide concentrations from plasma samples by high-performance liquid chromatography with ultraviolet/visible. The proposed method could be applied for therapeutic drug monitoring and pharmacokinetics studies of the four compounds throughout the treatment of tuberculosis patients., (© 2020 Wiley-VCH GmbH.)

We aimed to investigate the effect of interval between food intake and drug administration at fasting condition on the plasma concentrations of first-line anti- tuberculosis (TB) drugs in Chinese population. Newly diagnosed TB patients administered the anti-TB drugs under fasting conditions orally, and then had prepared breakfast at 30 minutes and 120 min after dosing, respectively. Blood sampling was also performed 120  minutes after dosing for the detection of Cmax purpose. Overall, twenty-five participants were included in our analysis. The Cmaxs of 30  minutes interval and 120  minutes interval were 21.8 ± 2.0 and 19.2 ± 2.0 μg/mL for rifampin, 1.6 ± 0.2 and 2.1 ± 0.2 μg/mL for isoniazid (INH), 1.5 ± 0.1and 1.5 ± 0.2 μg/mL for ethambutol (EMB), and 49.2 ± 3.7 and 41.5 ± 3.9 μg/mL for pyrazinamide, respectively. Statistical analysis revealed that there was no statistical difference between 2 groups. Additionally, 88.0% and 72.0% of the 25 participants at 2-hour interval group had peak concentrations less than the lower limit of the reference range for INH and EMB, respectively. The Cmaxs of INH were 0.9 ± 0.4 μg/ml for rapid acetylator, which was significantly lower than those of intermediate (1.4 ± 1.0 μg/mL), and slow acetylator (2.5 ± 1.0 μg/mL), respectively (P < .01). In conclusion, our data demonstrate that early food intake at 30 minutes after drug administration had no significant influence on the plasma concentrations. In addition, a high proportion of patients receiving first-line anti-TB regimen fail to achieve the expected plasma drug ranges of INH and EMB (P > .05).

Organic anion-transporting polypeptide (OATP) 1B induction is an evolving mechanism of drug disposition and interaction. However, there are contradictory reports describing OATP1B expression in hepatocytes and liver biopsies after administration of an inducer. This study investigated the in vivo effects of the common inducer rifampin (RIF) on the activity and expression of cynomolgus monkey OATP1B1 and OATP1B3 transporters, which are structurally and functionally similar their human OATP1B counterparts. Multiple doses of oral RIF (15 mg/kg) resulted in a steady 3.9-fold increase of CYP3A biomarker, 4 β -hydroxycholesterol (4 β HC), in the plasma samples collected before each RIF dose during the treatment period (i.e., predose). In contrast, the predose plasma levels of OATP1B biomarkers coproporphyrin (CP) I and CPIII did not change when compared with RIF treatment. The trough concentration, area under plasma concentration-time curve (AUC), and half-life of RIF decreased markedly during RIF treatment, suggesting that RIF induced its own clearance. Consequently, RIF treatment increased CPI and CPIII AUCs substantially after a single administration and, to a lesser extent, after multiple administrations compared with preadministration AUCs. In addition, OATP1B1 and OATP1B3 mRNA expressions were not modulated by RIF treatment (0.85-1.3-fold), whereas CYP3A8 expression was increased 3.7-5.0-fold, which correlated well with the predose levels of CP and 4 β HC. Rifampin treatment showed 2.0-3.3-fold increases in P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-associated protein 2 (MRP2) expression in the small intestine. Collectively, these findings indicate that monkey OATP1B and OATP1B3 are not induced by RIF, and further investigation of OATP1B induction by RIF and other nuclear receptor activators in humans is warranted. SIGNIFICANCE STATEMENT: In this study, combined endogenous biomarker and gene expression data suggested that RIF did not induce OATP1B in cynomolgus monkeys. For the first time, the study determines transporter gene expression in the nonhuman primate liver, gut, and kidney tissues after administration of RIF for 7 days, leading to a better understanding of the induction of OATP1B and other major drug transporters. Finally, it provides evidence to strengthen the claim that coproporphyrin is a suitable endogenous probe of OATP1B activity., (Copyright © 2020 by The American Society for Pharmacology and Experimental Therapeutics.)

In vitro permeability and in vivo pharmacokinetics of pemafibrate were investigated in human intestinal and animal models untreated or pretreated with cyclosporine A or rifampicin to evaluate any drug interactions. Ratios of basal to apical apparent permeability (P app ) over apical to basal P app in the presence of pH gradients decreased from 0.37 to 0.080 on rifampicin co-incubation, suggesting active transport of pemafibrate from basal to apical sides in intestinal models. Plasma concentrations of intravenously administered pemafibrate were enhanced moderately in control mice but only marginally in humanized-liver mice by oral pretreatment with rifampicin [an organic anion transporting polypeptide (OATP) 1B1 inhibitor] 1 h before the administration of pemafibrate. In three cynomolgus monkeys genotyped as wild-type OATP1B1 (2 homozygous and 1 heterozygous), oral dosing of cyclosporine A 4 h or rifampicin 1 h before pemafibrate administration significantly increased the areas under the plasma concentration-time curves (AUC) of intravenously administered pemafibrate by 4.9- and 7.4-fold, respectively. Plasma AUC values of three pemafibrate metabolites in cynomolgus monkeys were also increased by cyclosporine A or rifampicin. These results suggested that pemafibrate was actively uptaken in livers and rapidly cleared from plasma in cynomolgus monkeys; this rapid clearance was suppressible by OATP1B1 inhibitors., Competing Interests: Declaration of competing interest S.O. is a visiting scientist in academia and works for Kowa Co., the manufacturer of pemafibrate. The other authors declare that there are no conflicts of interest., (Copyright © 2020 The Japanese Society for the Study of Xenobiotics. Published by Elsevier Ltd. All rights reserved.)

Leprosy is a chronic infectious disease caused my Mycobacterium leprae that primarily affects peripheral nervous system and extremities and is prevalent in tropical countries. Treatment for leprosy with multidrug regimens is very effective compared to monotherapy especially in multibacillary cases. The three major antileprosy drugs currently in use are 4, 4'-diaminodiphenyl sulfone (DDS, dapsone), rifampicin, and clofazimine. During multidrug therapy, the potent antibiotic rifampicin induces the metabolism of dapsone, which results in decreased plasma half-life of dapsone and its metabolites. Furthermore, rifampicin induces its own metabolism and decreases its half-life during monotherapy. Rifampicin upregulates several hepatic microsomal drug-metabolizing enzymes, especially cytochrome P450 (CYP) family that in turn induce the metabolism of dapsone. Clofazimine lacks significant induction of any drug-metabolizing enzyme including CYP family and does not interact with dapsone metabolism. Rifampicin does not induce clofazimine metabolism during combination treatment. Administration of dapsone in the acetylated form (acedapsone) can release the drug slowly into circulation up to 75 days and could be useful for the effective treatment of paucibacillary cases along with rifampicin. This review summarizes the major aspects of antileprosy drug metabolism and drug interactions and the role of cytochrome P450 family of drug metabolizing enzymes, especially CYP3A4 during multidrug regimens for the treatment of leprosy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Rifampicin is a key component of treatment for tuberculosis and its efficacy is determined by the blood levels attained after therapeutic doses. However, there is a high variability of rifampicin blood levels that is related to both the patient and the formulation used. To date, the effect of diabetes mellitus on the plasma levels of rifampicin was low exploited, which could be relevant either by the significant increase of the comorbidity worldwide as by the probable influence of diabetes on the rifampicin exposure. The study aims to evaluate whether diabetes mellitus contribute to the variation of the maximum concentration of rifampicin in patients with tuberculosis treated with a daily dose of 10mg/kg. Rifampicin and glycated hemoglobin were measured by high-performance liquid chromatography, and blood glucose by spectrophotometry. A total of 62 male patients were included in the study, and 26 presented diabetes mellitus. Rifampicin plasma levels in 2-h plasma samples collected at day 61 ranged from 3μg/mL to 14.2μg/mL. Drugs levels were similar between diabetic and non-diabetic patients and were not correlated with blood glucose and glycated hemoglobin. Moreover, a high percentage of patients in both groups presented low levels of rifampicin., (Copyright © 2020 Sociedade Brasileira de Infectologia. Published by Elsevier España, S.L.U. All rights reserved.)

Background: Fluoroquinolones and rifampicin are antibiotics frequently used for the treatment of osteoarticular infections, and their therapeutic drug monitoring is recommended. The aim of this study was to develop and validate a rapid and selective method of simultaneous quantification of levofloxacin, ciprofloxacin, moxifloxacin and rifampicin with short pretreatment and run times in order to be easily used in clinical practice., Methods: After a simple protein precipitation of plasma samples, the chromatographic separation was performed using an ultra-performance liquid chromatography system coupled with mass tandem spectrometry in a positive ionization mode. The mobile phase consisted of a gradient elution of water-formic acid (100:0.1, v/v)-ammonium acetate 2 mM (A) and methanol-formic acid (100:0.1, v/v)-ammonium acetate 2 mM (B) at a flow rate at 0.3 mL/min., Results: Analysis time was 5 min per run, and all analytes and internal standards eluted within 0.85-1.69 minutes. The calibration curves were linear over the range from 0.5-30 μg/mL for levofloxacin, ciprofloxacin, moxifloxacin and rifampicin with linear regression coefficients above 0.995 for all analytes. The intra-day and inter-day coefficients of variation were below 10 % for lower and higher concentration. This method was successfully applied to drug monitoring in patients with an osteoarticular infection., Conclusion: A simple, rapid, and selective liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantification of levofloxacin, ciprofloxacin, moxifloxacin and rifampicin in human plasma., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

In this research, we developed and validated a liquid chromatography coupled to mass spectrometry (LC-QToF-MS) method for simultaneous quantification of the anti-tuberculosis drugs ethambutol, isoniazid, pyrazinamide and rifampicin in human plasma. Plasma samples spiked with cimetidine (internal standard) were extracted using protein precipitation with acetonitrile containing 1% formic acid. Separation was performed using a C 18 column under flow gradient conditions with water and acetonitrile, both containing 5 mm ammonium formate and 0.1% formic acid. The method was validated according to the ANVISA and US Food and Drug Administration guidelines for bioanalytical method validation. The calibration curve was linear over a concentration range of 0.2-5 μg ml -1 for ethambutol, 0.2-7.5 μg ml -1 for isoniazid, 1-40 μg ml -1 for pyrazinamide and 0.25-2 μg ml -1 for rifampicin, all with adequate precision and accuracy. The method was reproducible, selective and free of carryover and matrix effects. The validated LC-QToF-MS method was successfully applied to real samples and shown to be applicable to future therapeutic and pharmacokinetic monitoring studies., (© 2020 John Wiley & Sons, Ltd.)

Objective: P-glycoprotein (PGP) overexpression may be one of the operating mechanisms of suboptimal responses to antitubercular treatment (ATT) in patients with lymph node tuberculosis. This might become responsible for the development of drug resistance later due to exposure of subtherapeutic concentrations to the mycobacteria. In this study we aim to study the prevalence of PGP expression and function and its relationship with serum concentrations of Rifampicin in consecutive patients with lymph node tuberculosis., Methods: All newly diagnosed treatment naïve subjects with a confirmed diagnosis of tubercular lymphadenopathy were included in the study and the expression and function of PGP in blood was determined by flowcytometry at baseline and after two months of treatment. Serum levels of Rifampicin was measured at 2 months by high performance liquid chromatography (HPLC). The mean net PGP expression expressed as percent and relative fluorescence indices (RFI) of PGP expression and function respectively was compared at baseline at 2 months and was also correlated with serum rifampicin levels., Results: The mean net PGP expression, RFI of PGP expression and RFI of PGP function were significantly higher in patients with lymph node tuberculosis as compared to healthy controls and the mean net PGP expression and RFI of PGP expression were significantly higher at 2 months as compared to baseline (25.64 ± 5.18% vs. 27.68 ± 4.89%, 4.34 ± 1.09% vs. 4.95 ± 1.55). There was no significant difference in RFI of PGP expression and RFI of PGP function between the poor-responders and responders at baseline and 2 months however there was a trend towards significantly higher net PGP expression amongst poor responders at baseline. The mean serum rifampicin levels were 10.74 ± 2.36 μg/ml in the responder group and 7.86 ± 1.21 μg/ml in the non-responder group and the difference between the two was statistically significant (p = 0.004)., Conclusions: Overexpression of PGP is common in patients with lymph node tuberculosis and leads to lower concentrations of Rifampicin in blood which subsequently may give rise to development of drug resistance. This is also responsible for poor therapeutic responses in these patients. Nonspecific inhibitors of PGP may be used in conjunction with ATT to augment therapeutic response in such cases., Competing Interests: Conflicts of interest The authors have none to declare., (Copyright © 2019 Tuberculosis Association of India. Published by Elsevier B.V. All rights reserved.)

To address the most appropriate endogenous biomarker for drug-drug interaction risk assessment, eight healthy subjects received an organic anion transporting polypeptide 1B (OATP1B) inhibitor (rifampicin, 150, 300, and 600 mg), and a probe drug cocktail (atorvastatin, pitavastatin, rosuvastatin, and valsartan). In addition to coproporphyrin I, a widely studied OATP1B biomarker, we identified at least 4 out of 28 compounds (direct bilirubin, glycochenodeoxycholate-3-glucuronide, glycochenodeoxycholate-3-sulfate, and hexadecanedioate) that presented good sensitivity and dynamic range in terms of the rifampicin dose-dependent change in area under the plasma concentration-time curve ratio (AUCR). Their suitability as OATP1B biomarkers was also supported by the good correlation of AUC 0-24h between the endogenous compounds and the probe drugs, and by nonlinear regression analysis (AUCR -1 vs. rifampicin plasma C max (maximum total concentration in plasma)) to yield an estimate of the inhibition constant of rifampicin. These endogenous substrates can complement existing OATP1B-mediated drug-drug interaction risk assessment approaches based on agency guidelines in early clinical trials., (© 2019 The Authors. Clinical Pharmacology & Therapeutics published by Wiley Periodicals, Inc. on behalf of American Society for Clinical Pharmacology and Therapeutics.)

The most effective antituberculosis drug treatment regimen for tuberculous meningitis is uncertain. We conducted a randomized controlled trial comparing standard treatment with a regimen intensified by rifampin 15 mg/kg and levofloxacin for the first 60 days. The intensified regimen did not improve survival or any other outcome. We therefore conducted a nested pharmacokinetic/pharmacodynamic study in 237 trial participants to define exposure-response relationships that might explain the trial results and improve future therapy. Rifampin 15 mg/kg increased plasma and cerebrospinal fluid (CSF) exposures compared with 10 mg/kg: day 14 exposure increased from 48.2 hour·mg/L (range 18.2-93.8) to 82.5 hour·mg/L (range 8.7-161.0) in plasma and from 3.5 hour·mg/L (range 1.2-9.6) to 6.0 hour·mg/L (range 0.7-15.1) in CSF. However, there was no relationship between rifampin exposure and survival. In contrast, we found that isoniazid exposure was associated with survival, with low exposure predictive of death, and was linked to a fast metabolizer phenotype. Higher doses of isoniazid should be investigated, especially in fast metabolizers., (© 2020 The Authors. Clinical Pharmacology & Therapeutics published by Wiley Periodicals, Inc. on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Tuberculosis (TB) is the leading cause of death from a single infectious agent, requiring at least 6 months of multidrug treatment to achieve cure 1 . However, the lack of reliable data on antimicrobial pharmacokinetics (PK) at infection sites hinders efforts to optimize antimicrobial dosing and shorten TB treatments 2 . In this study, we applied a new tool to perform unbiased, noninvasive and multicompartment measurements of antimicrobial concentration-time profiles in humans 3 . Newly identified patients with rifampin-susceptible pulmonary TB were enrolled in a first-in-human study 4 using dynamic [ 11 C]rifampin (administered as a microdose) positron emission tomography (PET) and computed tomography (CT). [ 11 C]rifampin PET-CT was safe and demonstrated spatially compartmentalized rifampin exposures in pathologically distinct TB lesions within the same patients, with low cavity wall rifampin exposures. Repeat PET-CT measurements demonstrated independent temporal evolution of rifampin exposure trajectories in different lesions within the same patients. Similar findings were recapitulated by PET-CT in experimentally infected rabbits with cavitary TB and confirmed using postmortem mass spectrometry. Integrated modeling of the PET-captured concentration-time profiles in hollow-fiber bacterial kill curve experiments provided estimates on the rifampin dosing required to achieve cure in 4 months. These data, capturing the spatial and temporal heterogeneity of intralesional drug PK, have major implications for antimicrobial drug development.

With the increased cases of multidrug- or rifampicin-resistant tuberculosis and co-infection with HIV globally, it is difficult to achieve ideal clinical responses because of poor drug absorption and drug-drug interactions. Herein, a bioanalytical UPLC-MS/MS method was developed and validated to quantify five anti-TB agents in human plasma samples for detecting blood drug concentrations to improve therapeutic effects. To overcome the matrix effects, stable isotope labeled analogue of each analyte was used for internal standardization. A simple single-step protein precipitation by acetonitrile was employed for the sample preparation, then the analytes including rifampicin, rifabutin, pyrazinamid, ethambutol, isoniazid and their isotope labeled internal standards (ILISs) were implemented on an HILIC silica column with a gradient mode. The linear range for each analyte was covering the peak drug concentration (C max ) in the 20 times diluted plasma samples. The coefficient of variation of intra- and inter-day precision was less than 17.0 %, and the accuracy ranged between 91.5 and 110.0 %. The extraction recoveries of all agents were ≥90.2 %, and the matrix effects with internal standard-normalization for all agents were 97.1-110.0 %. The optimal blood sampling time was designed basing on the results of stability validation. This UPLC-MS/MS method with a run time of 3.5 min was successfully applied to routine therapeutic monitoring of the five anti-TB agents in patient plasma., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Rifampicin is a common antibiotic used in human and veterinary medicine to treat tuberculosis and other diseases caused by numerous pathogenic bacteria. However, the excessive or improper use of rifampicin usually leads to a series of problems, including bacterial resistance, excessive drug-resistance and water pollution. Thus, it is of great importance to develop selective and sensitive assays for monitoring rifampicin in biological systems. In this study, we designed a fluorescence "turn-off" strategy for the trace detection of rifampicin based on a glutathione-stabilized copper nanoclusters (GSH-Cu NC) sensor. In an aqueous solution, the fluorescence of the GSH-Cu NCs at 632 nm can be quenched effectively and selectively by rifampicin due to the inner-filter effect (IFE) of fluorescence mechanism. Distinctively, this GSH-Cu NC sensor exhibited excellent fluorescence sensing capability for the trace detection of rifampicin with a very low limit of detection (LOD) of 16 pM in a wide linear range from 50 to 10 000 pM. It is not only more sensitive than the other methods previously reported for the detection of rifampicin, but also has an outstanding selectivity and strong anti-interference in complex samples. Furthermore, the as-developed GSH-Cu NCs were also successfully applied to determine rifampicin in different real samples with quantitative spike recoveries ranging from 97% to 105%.

Background: Rifampicin is known to degrade at the acidic pH of the stomach, especially in the presence of isoniazid. Although isoniazid also degrades partially, its degradation is reversible., Objective: Presently, we provide a proof of the fact that the simultaneous oral administration of rifampicin (RIF), upon incorporation into solid lipid nanoparticles (RIF-SLNs), with isoniazid (INH) overcomes its INH-induced degradation and improves its oral bioavailability in rats., Methods: Solid lipid nanoparticles of RIF (RIF-SLNs) were prepared using a novel and patented method. The effect of INH was investigated on in vivo bioavailability of RIF both in its free and encapsulated (RIF-SLNs) form, after oral administration to rats., Results: C max and AUC 0-∞ of RIF increased 158 % and 125 %, respectively, upon incorporation into SLNs versus free RIF when combined with INH. The T max decreased from 5.67 h to 3.3 h, and the plasma concentration of RIF remained above its MIC (8 μg/ml) at all the tested time points starting with 15 min, when administered as RIF-SLNs in combination with INH., Conclusion: The results confirm the scope of combining RIF-SLNs with INH to overcome the bioavailability of free RIF when combined with INH, especially in fixed dose combinations., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: Diabetes mellitus (DM) is associated with poor TB treatment outcome. Previous studies examining the effect of DM on TB drug concentrations yielded conflicting results. No studies have been conducted to date in an African population., Objectives: To compare exposure to TB drugs in Tanzanian TB patients with and without DM., Patients and Methods: A prospective pharmacokinetic study was performed among 20 diabetic and 20 non-diabetic Tanzanian TB patients during the intensive phase of TB treatment. Plasma pharmacokinetic parameters of isoniazid, rifampicin, pyrazinamide and ethambutol were compared using an independent-sample t-test on log-transformed data. Multiple linear regression analysis was performed to assess the effects of DM, gender, age, weight, HIV status and acetylator status on exposure to TB drugs., Results: A trend was shown for 25% lower total exposure (AUC0-24) to rifampicin among diabetics versus non-diabetics (29.9 versus 39.9 mg·h/L, P=0.052). The AUC0-24 and peak concentration (Cmax) of isoniazid were also lower in diabetic TB patients (5.4 versus 10.6 mg·h/L, P=0.015 and 1.6 versus 2.8 mg/L, P=0.013). Pyrazinamide AUC0-24 and Cmax values were non-significantly lower among diabetics (P=0.08 and 0.09). In multivariate analyses, DM remained an independent predictor of exposure to isoniazid and rifampicin, next to acetylator status for isoniazid., Conclusions: There is a need for individualized dosing of isoniazid and rifampicin based on plasma concentration measurements (therapeutic drug monitoring) and for clinical trials on higher doses of these TB drugs in patients with TB and DM., (© The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Induction potentials of the pregnane X receptor (PXR) activator rifampin (RIF) on transporter genes [e.g., organic anion-transporting polypeptides (OATPs)] are still in its infancy or remain controversial in the field. The present investigations characterized changes in transporter gene expression by RIF in sandwich-cultured hepatocytes from multiple donors of human and cynomolgus monkey using real-time quantitative reverse transcription polymerase chain reaction method. Three-day treatment of RIF significantly induced CYP3A4 (∼60-fold induction), but not CYP1A2 and CYP2D6 genes. SLC51B was the most highly induced uptake transporter gene (>10-fold) in both human and monkey hepatocytes. A greater induction of CYP2C9 was observed in monkey hepatocytes than that in humans. ATP-binding cassette (ABC)B1 and ABCC2 were induced slightly above 2-fold in human and monkey hepatocytes and appeared to be dose-dependent. The induction of OATP and other transporter genes was generally less than 2-fold and considered not clinically relevant. SLCO2B1 was not detectable in monkey hepatocytes. To investigate in vivo OATP induction, RIF (18 mg/kg per day) was orally dosed to cynomolgus monkeys for 7 days. Pitavastatin and antipyrine were intravenously dosed before and after RIF treatment as exogenous probes of OATP and CYP activities, respectively. Plasma coproporphyrin-I (CP-I) and coproporphyrin-III (CP-III) were measured as OATP endogenous biomarkers. Although a significant increase of antipyrine clearance (CL) was observed after RIF treatment, the plasma exposures of pitavastatin, CP-I, and CP-III remained unchanged, suggesting that OATP function was not significantly altered. The results suggested that OATP transporters were not significantly induced by PXR ligand RIF. The data are consistent with current regulatory guidances that the in vitro characterization of transporter induction during drug development is not required. SIGNIFICANCE STATEMENT: Organic anion-transporting polypeptide (OATP) genes were not induced by rifampin in sandwich-cultured human and monkey hepatocytes OATP functions measured by OATP probe pitavastatin and endogenous marker coproporphyrins were not altered in monkeys in vivo by 7-day rifampin treatment. The data suggested that OATP transporters are unlikely induced by the pregnane X receptor ligand rifampin, which are consistent with current regulatory guidances that the in vitro characterization of OATP1B induction during drug development is not required., Competing Interests: The authors were all employees of Gilead Sciences during this research and declare no conflicts of interest., (Copyright © 2019 by The American Society for Pharmacology and Experimental Therapeutics.)

Background: The 24-h area under the concentration-time curve (AUC 24 )/minimal inhibitory concentration ratio is the best predictive pharmacokinetic/pharmacodynamic (PK/PD) parameter of the efficacy of first-line anti-tuberculosis (TB) drugs. An optimal sampling strategy (OSS) is useful for accurately estimating AUC 24 ; however, OSS has not been developed in the fed state or in the early phase of treatment for first-line anti-TB drugs., Methods: An OSS for the prediction of AUC 24 of isoniazid, rifampicin, ethambutol and pyrazinamide was developed for TB patients starting treatment. A prospective, randomized, crossover trial was performed during the first 3 days of treatment in which first-line anti-TB drugs were administered either intravenously or in fasting or fed conditions. The PK data were used to develop OSS with best subset selection multiple linear regression. The OSS was internally validated using a jackknife analysis and externally validated with other patients from different ethnicities and in a steady state of treatment., Results: OSS using time points of 2, 4 and 8 h post-dose performed best. Bias was < 5% and imprecision was < 15% for all drugs except ethambutol in the fed condition. External validation showed that OSS 2-4-8 cannot be used for rifampicin in steady state conditions., Conclusion: OSS at 2, 4 and 8 h post-dose enabled an accurate and precise prediction of AUC 24 values of first-line anti-TB drugs in this population., Trial Registration: ClinicalTrials.gov (NCT02121314).

Purpose: Optimization of antifungal therapy with voriconazole can be challenging due to inter- and intrapatient variability in voriconazole pharmacokinetics (PK). In this case, we introduce challenges in voriconazole therapy due to drug-drug interactions, autoinduction, and saturable metabolism., Summary: A 32-year-old male on chronic prednisone developed central nervous system (CNS) aspergillosis. He was started on high-dose intravenous (IV) voriconazole 8.5 mg/kg every 12 hours due to concerns for lasting induction effects of recent rifampin therapy. The initial voriconazole trough was 2 μg/mL. Frequent dose adjustments were made to maintain the therapeutic trough goal. On day 24 of voriconazole therapy, his trough was undetectable on IV voriconazole 5.5 mg/kg every 12 hours. His dose was escalated to 8.5 mg/kg every 12 hours to avoid subtherapeutic levels and therapeutic failure. On day 48, his trough level was 1.1 μg/mL on the same dose. His regimen was changed to 6.5 mg/kg every 8 hours at this point. Sixteen days after this regimen on day 74 of voriconazole therapy, his trough was 27.2 μg/mL indicating saturable PK of voriconazole in the absence of interacting drugs., Conclusion: Our findings highlight the unpredictable PK of voriconazole and reinforce the importance of continuous therapeutic drug monitoring in critically ill patients.

Background: Tuberculosis (TB) remains a critical infectious, contagious disease worldwide with high prevalence and mortality rate. The directly observed treatment short-course therapy includes rifampicin (RMP) and isoniazid (INH) for at least 6 months. The purposes of this scheme are to interrupt the transmissibility of the Mycobacterium tuberculosis complex and to avoid secondary complications. Low plasma concentrations of these anti-TB drugs have been associated with extended treatment duration, therapeutic failure, and relapse. The determination of anthropometric, genetic, and clinical variables that may affect plasma concentrations of RMP and INH might facilitate the detection of patients at increased risk of therapeutic failure., Methods: A prospective observational study was performed in patients with TB diagnosis. A fixed-dose combined formulation was administered following clinical guidelines, and 12 venous blood samples were collected within 24 hours after dose for the quantification of plasma levels of RMP and INH by high-performance liquid chromatography-ultraviolet. The plasma concentrations versus time for each drug in each patient were assessed by a noncompartmental approach to obtain Cmax, and the area under the concentration-time curve to the last observation point (AUC0-24 h) was calculated by the linear trapezoidal rule. Genetic polymorphisms of the enzyme involved in INH metabolism (NAT2) and proteins involved in RMP transport (glycoprotein-P and OATP1B1) were determined., Results: A total of 34 patients aged between 18 and 72 years with the diagnosis of TB were included in the current study. A multivariate analysis was performed to determine the anthropometric and genetic characteristics that modified the Cmax and AUC0-24 h of RMP and INH. Results indicated that RMP Cmax and AUC0-24 h were affected by sex, dose/weight, and single nucleotide polymorphism of MDR1. In addition, age, body mass index, and NAT2 acetylator genotype were shown to determine the Cmax and AUC0-24 h for INH., Conclusions: Anthropometric, genetic, and dosage characteristics of Mexican patients with TB are an important source of risk for subtherapeutic plasma concentrations of anti-TB drugs. Factors such as lower-than-recommended RMP dose, male patients with TB, and MDR1 3435 genotype, in addition to age group, body mass index, and INH acetylator phenotype based on NAT2 genotype, should be considered during treatment.

Therapeutic drug monitoring has been employed in anti-tuberculosis (TB) drugs to assess optimal dose for maximum therapeutic effects and minimal toxicity. But the determinants of serum concentration need further evidences.In a retrospective case-control study, clinical and laboratory data were collected from 717 in-patients with TB at Xi'an Chest Hospital, China. Two hours serum concentrations of isoniazid, rifampicin, pyrazinamide as well as ethambutol were obtained and analyzed by liquid chromatography-tandem mass spectrometry.The month 2 culture conversion group had lower concentration of isoniazid, pyrazinamide, and ethambutol than month 1 group. Statistical analysis showed that serum concentrations of isoniazid, rifampicin, pyrazinamide, and ethambutol revealed a positive relationship with dose (mg/kg) (P < .001, P < .001, P < .001, and P = .003, respectively). Furthermore, isoniazid concentration was related to smoking (P = .009) and prior TB (P = .011), while rifampicin and pyrazinamide concentrations were correlated to sex (P = .004 and 0.025, respectively). Ethambutol concentration was associated with creatinine clearance (Ccr, P = .002).It is necessary to optimize drug doses using therapeutic drug monitoring while considering the following determinants: weight, smoking status, prior TB, sex, and Ccr. Furthermore, low 2 hours serum concentrations can be associated with longer culture conversion.

Purpose: Cytochrome P450 (CYP) 3A plays an important role in the metabolism of many clinically used drugs and exhibits substantial between-subject variability (BSV) in activity. Current methods to assess variability in CYP3A activity have limitations and there remains a need for a minimally invasive clinically translatable strategy to define CYP3A activity. The purpose of this study was to evaluate the potential for a caffeine metabolic ratio to describe variability in CYP3A activity., Methods: The metabolic ratio 1,3,7-trimethyluric acid (TMU) to caffeine was evaluated as a biomarker to describe variability in CYP3A activity in a cohort (n = 28) of healthy 21 to 35-year-old males. Midazolam, caffeine, and TMU concentrations were assessed at baseline and following dosing of rifampicin (300 mg daily) for 7 days., Results: At baseline, correlation coefficients for the relationship between apparent oral midazolam clearance (CL/F) with caffeine/TMU ratio measured at 3, 4, and 6 h post dose were 0.82, 0.79, and 0.65, respectively. The strength of correlations was retained post rifampicin dosing; 0.72, 0.87, and 0.82 for the ratios at 3, 4, and 6 h, respectively. Weaker correlations were observed between the change in midazolam CL/F and change in caffeine/TMU ratio post/pre-rifampicin dosing., Conclusion: BSV in CYP3A activity was well described by caffeine/TMU ratios pre- and post-induction. The caffeine/TMU ratio may be a convenient tool to assess BSV in CYP3A activity, but assessment of caffeine/TMU ratio alone is unlikely to account for all sources of variability in CYP3A activity.

Objective: There is considerable uncertainty regarding the optimal use of rifampicin for the treatment of tuberculous (TB) meningitis. A pharmacokinetic modeling and simulation study of rifampicin concentrations in cerebrospinal fluid (CSF) during TB meningitis treatment was performed in this study., Methods: Parameters for rifampicin pharmacokinetics in CSF were estimated using individual-level rifampicin pharmacokinetic data, and the model was externally validated in three separate patient cohorts. Monte Carlo simulations of rifampicin serum and CSF concentrations were performed. The area under the rifampicin CSF concentration-versus-time curve during 24 h (AUC 0-24 ) relative to the minimum inhibitory concentration (MIC) served as the pharmacodynamic target., Results: Across all simulated patients on the first treatment day, 85% attained the target AUC 0-24 /MIC ratio of 30 under a weight-based dosing scheme approximating 10 mg/kg. At the rifampicin MIC of 0.5 mg/l, the probability of AUC 0-24 /MIC target attainment was 26%. With an intensified dosing strategy corresponding to 20 mg/kg, target attainment increased to 99%, including 93% with a MIC of 0.5 mg/l., Conclusions: Under standard dosing guidelines, few TB meningitis patients would be expected to attain therapeutic rifampicin exposures in CSF when the MIC is ≥0.5 mg/l. Either downward adjustment of the rifampicin MIC breakpoint in the context of TB meningitis, or intensified rifampicin dosing upwards of 20 mg/kg/day, would reflect the likelihood of pharmacodynamic target attainment in CSF., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background and Objective: This study proposes a model-informed approach for therapeutic drug monitoring (TDM) of rifampicin to improve tuberculosis (TB) treatment., Methods: Two datasets from pulmonary TB patients were used: a pharmacokinetic study (34 patients, 373 samples), and TDM data (96 patients, 391 samples) collected at Radboud University Medical Center, The Netherlands. Nine suitable population pharmacokinetic models of rifampicin were identified in the literature and evaluated on the datasets. A model developed by Svensson et al. was found to be the most suitable based on graphical goodness of fit, residual diagnostics, and predictive performance. Prediction of individual area under the concentration-time curve from time zero to 24 h (AUC 24 ) and maximum concentration (C max ) employing various sampling strategies was compared with a previously established linear regression TDM strategy, using sampling at 2, 4, and 6 h, in terms of bias and precision (mean error [ME] and root mean square error [RMSE])., Results: A sampling strategy using 2- and 4-h blood collection was selected to be the most suitable. The bias and precision of the two strategies were comparable, except that the linear regression strategy was more biased in prediction of the AUC 24  than the model-informed approach (ME of 9.9% and 1.5%, respectively). A comparison of resulting dose advice, using predictions on a simulated dataset, showed no significant difference in sensitivity or specificity between the two methods. The model was successfully implemented in the InsightRX precision dosing platform., Conclusion: Blood sampling at 2 and 4 h, combined with model-based prediction, can be used instead of the currently used linear regression strategy, shortening the sampling by 2 h and one sampling point without performance loss while simultaneously offering flexibility in sampling times.

Determining the optimal dosages of isoniazid, rifampicin, pyrazinamide and ethambutol in children is necessary to obtain therapeutic serum concentrations of these drugs. Revised dosages have improved the exposure of 1st line anti-tubercular drugs to some extent; there is still scope for modification of the dosages to achieve exposures which can lead to favourable outcome of the disease. High dose of rifampicin is being investigated in clinical trials in adults with some benefit; studies are required in children. Inter-individual pharmacokinetic variability and the effect of age, nutritional status, Human immunodeficiency virus (HIV) infection, acetylator genotype may need to be accounted for in striving for the dosages best suited for an individual.

Background: Recent evidence suggests that higher rifampicin doses may improve tuberculosis (TB) treatment outcome., Methods: In this observational cohort study we evaluated all TB patients who were treated with high-dose rifampicin (> 10 mg/kg daily) in our reference centre, from January 2008 to May 2018. Indications, achieved plasma rifampicin exposures, safety and tolerability were evaluated., Results: Eighty-eight patients were included. The main indications were low plasma concentrations (64.7%) and severe illness (29.5%), including central nervous system TB. Adjusted rifampicin dosages ranged from 900 mg to a maximum of 2400 mg (corresponding to 32 mg/kg) per day. Patients with severe illness received high-dose rifampicin immediately, the others had a higher dosage guided by therapeutic drug monitoring. Four patients developed hepatotoxicity, of which two were proven due to isoniazid. Re-introduction of high-dose rifampicin was successful in all four. Eighty-seven patients tolerated high-dose rifampicin well throughout treatment. Only one patient required a dose reduction due to gastro-intestinal disturbance., Conclusion: High-dose rifampicin, used in specific groups of patients in our clinical setting, is safe and well-tolerated for the whole treatment duration. Measurement of drug exposures could be used as a tool/guide to increase rifampicin dosage if a reduced medication absorption or a poor treatment outcome is suspected. We suggest to administer high-dose rifampicin to patients with severe manifestations of TB or low rifampicin exposure to improve treatment outcome., Competing Interests: The authors have declared that no competing interests exist.

Rifampicin is used in both phases of treatment for tuberculosis. In chronic use, the short half-life and the self-induction of metabolism can decrease the levels of the drug below the minimal inhibitory concentration. The aim of the study was to investigate whether plasma concentrations of rifampicin are sustained above 0.5μg/mL in patients with tuberculosis using 600mg/day. Rifampicin was measured in plasma by high-performance liquid chromatography and a sputum smear microscopy was performed in all days of the study. A total of 44 male patients completed the study. On days 31, 61 and 91, the mean plasma concentrations of rifampicin were 0.6 (0.5)μg/mL, 0.55 (0.5)μg/mL and 0.46 (0.4)μg/mL. There was a high variation of rifampicin levels leading to a high percentage of samples with concentrations below 0.5μg/mL. There was no significant association between the frequency of samples with drug levels below 0.5μg/mL with the conversion of the sputum microscopy. These data suggest that pre-doses samples offer limited information on the exposure of M. tuberculosis to rifampicin., (Copyright © 2019 Sociedade Brasileira de Infectologia. Published by Elsevier España, S.L.U. All rights reserved.)

The pharmacokinetic (PK) and clinical implications of combining metformin with rifampicin are relevant to increasing numbers of patients with diabetic tuberculosis (TB) across the world and are yet unclear. We assessed the impact of rifampicin on metformin PKs and its glucose-lowering effect in patients with diabetic TB by measuring plasma metformin and blood glucose during and after TB treatment. Rifampicin increased metformin exposure: plasma area under the plasma concentration-time curve from time point 0 to the end of the dosing interval (AUC 0-τ ) and peak plasma concentration (C max ) geometric mean ratio (GMR; during vs. after TB treatment) were 1.28 (90% confidence interval (CI) 1.13-1.44) and 1.19 (90% CI 1.02-1.38; n = 22). The metformin glucose-lowering efficacy did not change (Δglucose - C max ; P = 0.890; n = 18). Thus, we conclude that additional glucose monitoring in this population is not warranted. Finally, 57% of patients on metformin and rifampicin, and 38% of patients on metformin alone experienced gastrointestinal adverse effects. Considering this observation, we advise patients to take metformin and rifampicin with food and preferably separated in time. Clinicians could consider metoclopramide if gastrointestinal adverse effects occur., (© 2018 The Authors Clinical Pharmacology & Therapeutics published by Wiley Periodicals, Inc. on behalf of American Society for Clinical Pharmacology and Therapeutics.)

CYP3A probe drugs such as midazolam and endogenous markers, and plasma 4β-hydroxycholesterol (4β-OHC) and urinary 6β-hydroxycortisol-to-cortisol ratios (6β-OHC/C) have been used as markers of CYP3A induction in cynomolgus monkeys, as with humans. However, there is limited information on their sensitivity and ability to detect CYP3A induction, as most studies were evaluated only at a high dose of the inducer, rifampicin (RIF; 20 mg/kg). In the present study, the CYP3A induction by RIF over a range doses of 0.2, 2 and 20 mg/kg (n = 4) was examined using CYP3A probe drugs (midazolam, triazolam and alprazolam) and the plasma and urinary endogenous CYP3A markers (4β-OHC and 6β-OHC/C). The sensitivity and relationship for detecting CYP3A induction was compared among the markers. Four days repeated oral administration of rifampicin to cynomolgus monkeys reduced the area under the plasma concentration-time curve of all CYP3A probe drugs in a rifampicin dose-dependent manner. Although the endogenous CYP3A markers (4β-OHC and 6β-OHC/C) were also changed for the middle (2 mg/kg) and high (20 mg/kg) doses of rifampicin, the fold-changes were relatively small, and CYP3A induction could not be detected at the lowest dose of rifampicin (0.2 mg/kg). In conclusion, CYP3A probe drugs are more sensitive for detecting CYP3A induction than endogenous CYP3A markers in cynomolgus monkeys, even for a short experimental period., (© 2019 John Wiley & Sons, Ltd.)

Drug-induced liver injury (DILI) is a common side effect of several medications and is considered a major factor responsible for the discontinuation of drugs during their development. Cholestasis is a DILI that results from impairment of bile acid transporters, such as the bile salt export pump (BSEP), leading to accumulation of bile acids. Both in vitro and in vivo studies are required to predict the risk of drug-induced cholestasis. In the present study, we used chimeric mice with humanized liver as a model to study drug-induced cholestasis. Administration of a single dose of ketoconazole or rifampicin, known to potentially cause cholestasis by inhibiting BSEP, did not result in elevated levels of alkaline phosphatase (ALP), which are known hepatic biomarkers. The concentration of taurodeoxycholic acid increased in the liver after ketoconazole administration, whereas rifampicin resulted in increased tauromuricholic acid and taurocholic acid (TCA) levels in the liver and plasma. Furthermore, rifampicin resulted in an increase in the uniform distribution of a compound with m/z 514.3, presumed as TCA through imaging mass spectrometry. The mRNA levels of bile acid-related genes were also altered after treatment with ketoconazole or rifampicin. We believe these observations to be a part of a feedback mechanism to decrease bile acid concentrations. The changes in bile acid concentrations results may reflect the initial responses of the human body to cholestasis. Furthermore, these findings may contribute to the screening of drug candidates, thereby avoiding drug-induced cholestasis during clinical trials and drug development.

A new carbon paste electrode for rifampicin (RIF) drug was prepared and fully characterized in terms of composition, usable pH range and temperature. The sensor is based on 2-hydroxypropyl β-cyclodextrin as a good ionophore in the carbon paste matrix. The modified electrode showed a Nernstian slope of 59.2 mV/decade over the concentration range of 3.2 × 10 -8 to 2.2 × 10 -4  M with a limit of detection 2.3 × 10 -8  M. The electrode has a short and stable response time of 4 s. The sensor manifested advantages of simple design, low cost, wide concentration range, excellent selectivity to rifampicin, applicable as an indicator electrode and renewability. The sensor was successfully used for determination of rifampicin in tablet and blood serum samples. Temperature dependence of the sensor potential response was examined in the temperature range of 15-55 °C. The sensor showed a very low thermal coefficient within the studied temperature range., (Copyright © 2018 Elsevier B.V. All rights reserved.)

We evaluated the effects of rifampin coadministration and MDR1 single nucleotide polymorphisms on the disposition of daptomycin in twelve healthy adults. There were no significant changes from baseline in the clearance (0.53 versus 0.55 liters/h, P =  1.00), volume of distribution (7.0 versus 7.2 liter, P =  0.62), or half-life (9.7 versus 9.6 h, P =  0.89) of daptomycin after exposure to rifampin. The tested MDR1 polymorphisms were not associated with significant differences in daptomycin disposition., (Copyright © 2018 American Society for Microbiology.)

The lack of available antibiotics is a global public health problem due to the emergence of antimicrobial resistance. Effective therapeutic regimens are urgently needed against Escherichia coli strains that produce the colistin resistance gene mcr-1 and to inhibit the emergence of resistance. In this study, we assessed the antimicrobial activity of a series of concentrations of colistin-based combinations with rifampin and/or azithromycin against three strains of Escherichia coli , including colistin-resistant isolate MZ1501 R , isolate HE1704 R that produces MCR-1, and colistin-susceptible isolate MZ1509 S Experiments were conducted with a medium inoculum of ∼10 7 CFU/ml over 48 h. Subsequently, the in vivo therapeutic effect was investigated using a neutropenic mouse thigh infection model. Almost all monotherapies showed unsatisfactory antibacterial activity against E. coli isolates producing MCR-1. In contrast, colistin in combination with rifampin or azithromycin resulted in an obvious decrease in the bacterial burden albeit with regrowth. More obviously, synergistic antimicrobial activity of colistin-based triple-combination therapy with rifampin and azithromycin was observed, resulting in a rapid and exhaustive antibacterial effect. In vivo treatments confirmed these findings, where mean decreases of 0.38 to 0.90 log 10 CFU and 1.27 to 1.78 log 10 CFU were noted after 24 h and 48 h of treatment, respectively, against colistin-resistant E. coli strains when 5 mg/kg of body weight of colistin was combined with rifampin and azithromycin. Colistin-based combinations with rifampin and azithromycin provide a more active therapeutic regimen than monotherapy or colistin-based double combinations against E. coli producing MCR-1., (Copyright © 2018 American Society for Microbiology.)

High doses of rifampin may help patients with tuberculous meningitis (TBM) to survive. Pharmacokinetic pharmacodynamic evaluations suggested that rifampin doses higher than 13 mg/kg given intravenously or 20 mg/kg given orally (as previously studied) are warranted to maximize treatment response. In a double-blind, randomized, placebo-controlled phase II trial, we assigned 60 adult TBM patients in Bandung, Indonesia, to standard 450 mg, 900 mg, or 1,350 mg (10, 20, and 30 mg/kg) oral rifampin combined with other TB drugs for 30 days. The endpoints included pharmacokinetic measures, adverse events, and survival. A double and triple dose of oral rifampin led to 3- and 5-fold higher geometric mean total exposures in plasma in the critical early days (2 ± 1) of treatment (area under the concentration-time curve from 0 to 24 h [AUC 0-24 ], 53.5 mg · h/liter versus 170.6 mg · h/liter and 293.5 mg · h/liter, respectively; P  < 0.001), with proportional increases in cerebrospinal fluid (CSF) concentrations and without an increase in the incidence of grade 3 or 4 adverse events. The 6-month mortality was 7/20 (35%), 9/20 (45%), and 3/20 (15%) in the 10-, 20-, and 30-mg/kg groups, respectively ( P  = 0.12). A tripling of the standard dose caused a large increase in rifampin exposure in plasma and CSF and was safe. The survival benefit with this dose should now be evaluated in a larger phase III clinical trial. (This study has been registered at ClinicalTrials.gov under identifier NCT02169882.)., (Copyright © 2018 American Society for Microbiology.)

Organic anion-transporting polypeptides (OATPs) mediate the uptake of various drugs from blood into the liver in the basolateral membrane of hepatocytes. Positron emission tomography (PET) is a potentially powerful tool to assess the activity of hepatic OATPs in vivo, but its utility critically depends on the availability of transporter-selective probe substrates. We have shown before that among the three OATPs expressed in hepatocytes (OATP1B1, OATP1B3, and OATP2B1), [ 11 C]erlotinib is selectively transported by OATP2B1. In contrast to OATP1B1 and OATP1B3, OATP2B1 has not been thoroughly explored yet, and no specific probe substrates are currently available. To assess if the prototypical OATP inhibitor rifampicin can inhibit liver uptake of [ 11 C]erlotinib in vivo, we performed [ 11 C]erlotinib PET scans in six healthy volunteers without and with intravenous pretreatment with rifampicin (600 mg). In addition, FVB mice underwent [ 11 C]erlotinib PET scans without and with concurrent intravenous infusion of high-dose rifampicin (100 mg/kg). Rifampicin caused a moderate reduction in the liver distribution of [ 11 C]erlotinib in humans, while a more pronounced effect of rifampicin was observed in mice, in which rifampicin plasma concentrations were higher than in humans. In vitro uptake experiments in an OATP2B1-overexpressing cell line indicated that rifampicin inhibited OATP2B1 transport of [ 11 C]erlotinib in a concentration-dependent manner with a half-maximum inhibitory concentration of 72.0 ± 1.4 μM. Our results suggest that rifampicin-inhibitable uptake transporter(s) contributed to the liver distribution of [ 11 C]erlotinib in humans and mice and that [ 11 C]erlotinib PET in combination with rifampicin may be used to measure the activity of this/these uptake transporter(s) in vivo. Furthermore, our data suggest that a standard clinical dose of rifampicin may exert in vivo a moderate inhibitory effect on hepatic OATP2B1.

This study evaluated coproporphyrin I (CPI) as a selective endogenous biomarker of OATP1B-mediated drug-drug interactions (DDIs) relative to clinical probe rosuvastatin using nonlinear mixed-effect modeling. Plasma and urine CPI data in the presence/absence of rifampicin were modeled to describe CPI synthesis, elimination clearances, and obtain rifampicin in vivo OATP Ki. The biomarker showed stable interoccasion baseline concentrations and low interindividual variability (<25%) in subjects with wildtype SLCO1B1. Biliary excretion was the dominant CPI elimination route (maximal >85%). Estimated rifampicin in vivo unbound OATP Ki (0.13 μM) using CPI data was 2-fold lower relative to rosuvastatin. Model-based simulations and power calculations confirmed sensitivity of CPI to identify moderate and weak OATP1B inhibitors in an adequately powered clinical study. Current analysis provides the most detailed evaluation of CPI as an endogenous OATP1B biomarker to support optimal DDI study design; further pharmacogenomic and DDI data with a panel of inhibitors are required., (© 2017 The Authors Clinical Pharmacology & Therapeutics published by Wiley Periodicals, Inc. on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Background: Dried blood spot (DBS) sampling for pharmacokinetic (PK) studies and therapeutic drug monitoring have unique advantages over venous sampling. This study aimed to evaluate a DBS method for first-line anti-tuberculosis drugs in children, and DBS sampling to assess PK parameters., Methods: Paraguayan children were treated according to the revised paediatric dosing scheme of the World Health Organization. A PK curve was performed both with DBS sampling and conventional venous sampling for rifampicin, pyrazinamide and ethambutol. Passing-Bablok regression, Bland-Altman plots and predictive performance evaluation were used to assess agreement between DBS and plasma concentrations. The percentages of patients attaining population PK values for C max and AUC 0-24h were calculated., Results: After use of a conversion factor, Passing-Bablok regression showed no significant proportional or systematic bias between DBS and plasma concentrations. Bland-Altman plots showed that 95% of the ratios of the DBS predicted:observed plasma concentrations lay between 0.6 and 1.4 for rifampicin, 0.5 and 1.6 for pyrazinamide and -0.4 and 2.8 for ethambutol. DBS measurements showed acceptable predictive performance for rifampicin and pyrazinamide, but not for ethambutol. Assessment of C max target attainment was 62.5% for isoniazid, 25% for rifampicin, 100% for pyrazinamide and 75% for ethambutol., Conclusion: For rifampicin and pyrazinamide, the DBS method was accurate in predicting plasma concentrations, and was used successfully for PK parameter assessment. However, predicting ethambutol plasma concentrations with DBS measurement was associated with too much imprecision. Despite higher dosing, only 25% of the population reached average target adult rifampicin exposures., (Copyright © 2018. Published by Elsevier B.V.)

Purpose: Cytochrome P450 (CYP) 3A4 is responsible for the metabolism of more than 30% of clinically used drugs. Inherent between subject variability in clearance of CYP3A4 substrates is substantial; by way of example, midazolam clearance varies by > 10-fold between individuals before considering the impact of extrinsic factors. Relatively little is known about inter-racial variability in the activity of this enzyme., Methods: This study assessed inter-racial variability in midazolam exposure in a cohort (n = 30) of CYP3A genotyped, age-matched healthy males of Caucasian and South Asian ancestries. Midazolam exposure was assessed at baseline, following 7 days of rifampicin and following 3 days of clarithromycin., Results: The geometric mean baseline midazolam area under the plasma concentration curve (AUC 0-6 ) in Caucasians (1057 μg/L/min) was 27% greater than South Asians (768 μg/L/min). Similarly, the post-induction midazolam AUC 0-6 in Caucasians (308 μg/L/min) was 50% greater than South Asians (154 μg/L/min), while the post-inhibition midazolam AUC 0-6 in Caucasians (1834 μg/L/min) was 41% greater than South Asians (1079 μg/L/min). The difference in baseline AUC 0-6 between Caucasians and South Asians was statistically significant (p ≤ 0.05), and a trend toward significance (p = 0.067) was observed for the post-induction AUC 0-6 ratio, in both unadjusted and genotype adjusted analyses., Conclusions: Significantly higher midazolam clearance was observed in healthy age-matched males of South Asian compared to Caucasian ancestry that was not explained by differences in the frequency of CYP3A genotypes.

Background: Standard treatment of foals with severe abscessing lung infection caused by Rhodococcus equi using rifampicin and a macrolide antibiotic can be compromised by extensive inhibition and/or induction of drug metabolising enzymes (e.g. CYP3A4) and transport proteins (e.g. P-glycoprotein), as has been shown for rifampicin and clarithromycin. The combination of rifampicin with the new, poorly metabolised gamithromycin, a long-acting analogue of azithromycin and tulathromycin with lower pharmacokinetic interaction potential, might be a suitable alternative., Objectives: To evaluate the pharmacokinetic interactions and pulmonary distribution of rifampicin and gamithromycin in healthy foals, and to investigate the cellular uptake of gamithromycin in vitro., Study Design: Controlled, four-period, consecutive, single-dose and multiple-dose study., Methods: Pharmacokinetics and lung distribution of rifampicin (10 mg/kg) and gamithromycin (6 mg/kg) were measured in nine healthy foals using LC-MS/MS. Enzyme induction was confirmed using the 4β-OH-cholesterol/cholesterol ratio. Affinity of gamithromycin to drug transport proteins was evaluated in vitro using equine hepatocytes and MDCKII-cells stably transfected with human OATP1B1, OATP1B3 and OATP2B1., Results: Rifampicin significantly (P<0.05) increased the plasma exposure of gamithromycin (16.2 ± 4.77 vs. 8.57 ± 3.10 μg × h/mL) by decreasing the total body clearance. Otherwise, gamithromycin significantly lowered plasma exposure of single- and multiple-dose rifampicin (83.8 ± 35.3 and 112 ± 43.1 vs. 164 ± 96.7 μg × h/mL) without a change in metabolic ratio and half-life. Gamithromycin was identified as an inhibitor of human OATP1B1, OATP1B3 and OATP2B1 and as a substrate of OATP2B1. In addition, it was extracted by equine hepatocytes via a mechanism which could be inhibited by rifampicin., Main Limitations: Influence of gamithromycin on pulmonary distribution of rifampicin was not evaluated., Conclusion: The plasma exposure of gamithromycin is significantly increased by co-administration of rifampicin which is most likely caused by inhibition of hepatic elimination., (© 2017 EVJ Ltd.)

Background: Measurement of rifampin levels is not part of routine practice. However, low levels are associated with failure of tuberculosis treatment. The clinical relevance of serum levels in daily practice is unclear. The objective was to evaluate rifampin serum concentrations and factors associated with insufficient concentrations., Methods: Patients with at least one rifampin concentration drawn 3 hours after intake (C3) between 2005 and 2014 were included. Data on demographic and clinical characteristics were collected, including side effects and dose adjustments. Two different criteria were used to define adequate concentrations (criterion 1: C3 a nd C 6 ≥ 3 mg/l; criterion 2: C3 or C6 ≥ 5 mg/l)., Results: Of 63 patients, 66% and 76% had a sufficient level according to criterion 1 or 2, respectively. C3 exceeded C6 in most patients, while a late maximum was significantly associated with diabetes mellitus (p = 0.003). A dose adjustment was made in 19% of cases, more frequently in patients with insufficient levels (p = 0.02) or with ≥ 2 side effects (p = 0.03)., Conclusion: Rifampin levels varied but were mostly adequate and a single measurement at 3 hours after intake provided the required information in most cases, indicating that full AUC0-24 measurements could be limited to specific situations.

Purpose: To evaluate association of the dose-dependent effect of rifampicin, an OATP1B inhibitor, on the plasma concentration-time profiles among OATP1B substrates drugs and endogenous substrates., Methods: Eight healthy volunteers received atorvastatin (1 mg), pitavastatin (0.2 mg), rosuvastatin (0.5 mg), and fluvastatin (2 mg) alone or with rifampicin (300 or 600 mg) in a crossover fashion. The plasma concentrations of these OATP1B probe drugs, total and direct bilirubin, glycochenodeoxycholate-3-sulfate (GCDCA-S), and coproporphyrin I, were determined., Results: The most striking effect of 600 mg rifampicin was on atorvastatin (6.0-times increase) and GCDCA-S (10-times increase). The AUC 0-24h of atorvastatin was reasonably correlated with that of pitavastatin (r 2  = 0.73) and with the AUC 0-4h of fluvastatin (r 2  = 0.62) and sufficiently with the AUC 0-24h of rosuvastatin (r 2  = 0.32). The AUC 0-24h of GCDCA-S was reasonably correlated with those of direct bilirubin (r 2  = 0.74) and coproporphyrin I (r 2  = 0.78), and sufficiently with that of total bilirubin (r 2  = 0.30). The AUC 0-24h of GCDCA-S, direct bilirubin, and coproporphyrin I were reasonably correlated with that of atorvastatin (r 2  = 0.48-0.70) [corrected]., Conclusion: These results suggest that direct bilirubin, GCDCA-S, and coproporphyrin I are promising surrogate probes for the quantitative assessment of potential OATP1B-mediated DDI.

Suboptimal plasma drug concentrations in antitubercular therapy (ATT) may lead to delayed treatment response and the emergence of acquired drug resistance. This study aimed (i) to determine and compare plasma concentrations of isoniazid (INH) and rifampicin (RIF) in children treated for tuberculosis receiving a daily or intermittent ATT regimen and (ii) to study the effect of INH and RIF exposure on clinical outcome at the end of therapy (EOT). A total of 41 children aged 2-16 years initiated on either a daily or three-times weekly (intermittent) ATT regimen were recruited into the study. Towards the end of the intensive phase, blood specimens were collected pre-dose and at 0.5, 1, 1.5, 2, 2.5, 4 and 6 h post-dose. Concentrations of INH and RIF were analysed using validated liquid chromatography-tandem mass spectrometry and high-performance liquid chromatography assays, respectively. The maximum plasma concentration (C max ), the area under the concentration-time curve from 0-6 h (AUC 0-6h ) and treatment outcome were determined. Ninety-two percent of patients had an INH C max  > 3 µg/mL. Seventy-seven percent of patients had a RIF C max  < 8 µg/mL and 28% of patients had a RIF AUC 0-24h  < 13 mg ⋅ h/L. INH and RIF exposure did not differ between daily and intermittent ATT regimens on the day of administration. All children had a favourable outcome at EOT. Since 77% of children had low RIF exposure, we recommend routine use of therapeutic drug monitoring to prevent relapse and to support implementation of the revised RNTCP 2012 doses., (Copyright © 2017 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.)