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Background: Severe acute malnutrition (SAM) may alter the pharmacokinetics (PK), efficacy, and safety of antiretroviral therapy. The phase IV study, IMPAACT P1092, compared PK, safety, and tolerability of zidovudine (ZDV), lamivudine (3TC), and lopinavir/ritonavir (LPV/r) in children with and without SAM., Materials and Methods: Children living with HIV 6 to <36 months of age with or without World Health Organization (WHO)-defined SAM received ZDV, 3TC, and LPV/r syrup for 48 weeks according to WHO weight band dosing. Intensive PK sampling was performed at weeks 1, 12, and 24. Plasma drug concentrations were measured using liquid chromatography tandem mass spectrometry. Steady-state mean area under the curve (AUC0-12h) and clearance (CL/F) for each drug were compared. Grade ≥3 adverse events were compared between cohorts., Results: Fifty-two children were enrolled across 5 sites in Africa with 44% (23/52) female, median age 19 months (Q1, Q3: 13, 25). Twenty-five children had SAM with entry median weight-for-height Z-score (WHZ) -3.4 (IQR -4.0, -3.0) and 27 non-SAM had median WHZ -1.0 (IQR -1.8, -0.1). No significant differences in mean AUC0-12h or CL/F were observed (P ≥ 0.09) except for lower 3TC AUC0-12h (GMR, 0.60; 95% CI, 0.4-1.0; P = 0.047) at week 12, higher ZDV AUC0-12h (GMR, 1.52; 1.2-2.0; P = 0.003) at week 24 in the SAM cohort compared with non-SAM cohort. Treatment-related grade ≥3 events did not differ significantly between cohorts (24.0% vs. 25.9%)., Conclusion: PK and safety findings for ZDV, 3TC, and LPV/r support current WHO weight band dosing of syrup formulations in children with SAM., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: For the treatment of HIV-1-related brain disease and for the prevention of the brain becoming a viral reservoir, it is important that antiretroviral agents reach sufficient concentrations in the CNS. To date, human brain pharmacokinetic data are solely derived from lumbar cerebrospinal fluid (CSF) and mostly originate from single samples., Design: We determined concentrations of antiretroviral drugs in serial samples of ventricular CSF and compared these to the concentrations in serum and lumbar CSF of these patients., Methods: Two treatment-naïve HIV-1-infected patients received external ventricular drainage for obstructive hydrocephalus. Starting with a combination antiretroviral regimen (cART), ventricular CSF, and subsequently lumbar CSF, with parallel serum, was frequently collected. Drug concentrations were determined and CSF-to-serum ratios were calculated., Results: High concentrations, resulting in high CSF-to-serum ratios, were found in the ventricular CSF of the three substances zidovudine, lamivudine and indinavir, whereas this was not observed for stavudine, ritonavir, saquinavir and efavirenz. Concentrations of zidovudine and lamivudine were up to four times greater in CSF from the ventricles than in lumbar CSF of the same patient. The zidovudine concentrations in the ventricular CSF exceeded serum concentrations by a factor of 1.4., Conclusion: Unexpectedly high concentrations of some antiretrovirals in the ventricular CSF, the site close to the brain parenchyma where HIV is located, should be considered when the cART regimen is aiming at CNS viral replication.

Simultaneous therapeutic drug monitoring (TDM) of combination antiretroviral therapy (cART) is critical during pregnancy in order to improve clinical follow-up, monitor viral load, and patient adherence to treatment.A modified simple and fast ultra-high performance liquid chromatography coupled with tandem mass spectrometry and electrospray ionization (UPLC-ESI-MS/MS) method was developed and validated according to national and international guidelines for the simultaneous determination of lamivudine (LMV), zidovudine (ZDV), lopinavir (LPV), and ritonavir (RTV) concentrations in 100-μL plasma sample of Human Immunodeficiency Virus (HIV)-positive pregnant women. Protein precipitation using 0.1% formic acid in cold acetonitrile was used for sample preparation. The chromatographic separation was achieved with a run-time of 3.0 minutes and 3-μL injection on an ethylene bridged hybrid C18 column (2.1 μm × 50 mm, 1.7 μm), under gradient conditions using acetonitrile and formic acid (0.1%).The chromatographic method was used to analyze 10 plasma samples from 8 HIV pregnant women as a clinical patient routinely follow-up by applying TDM criteria.The protonated precursor/product ion transitions for LMV (230.18/112.08), ZDV (268.22/127.10), LPV (629.55/447.35), and RTV (721.50/296.20) were recorded in multiple-reaction-monitoring (MRM) mode. The calibration curve was linear in the range of 50-3,000, 75-4,500, 250-15,000, and 25-1,500-ng/mL for LMV, ZDV, LPV, and RTV, respectively. The range of accuracy was 97.2% to 100.1% and precision 3.4% to 12.7%. The method showed specificity and matrix effect values of < 15%. Minimum absolute recovery percentages (%CV) were 90.5 (5.4), 90.8 (5.0), 95.4 (3.5), and 93.7 (6.9), for LMV, ZDV, LPV, and RTV, respectively. Drug concentrations in patient samples had high inter-individual variability with %CV of 91.98%, 77.54%, 53.80%, and 92.16% for ZDV, LMV, LPV, and RTV, respectively. Two of the 8 patients showed no adherence due to the absence of Protease Inhibitors (PIs) levels in plasma.This technique demonstrated to be effective in therapeutic drug monitoring and is intended to be used in population pharmacokinetics specifically for HIV-positive pregnant women.

Shenlin Fuzheng Capsule (SLFZC) is a herbal preparation used for HIV/AIDS in Guangxi, China. This study was designed to evaluate the influence of SLFZC on the pharmacokinetics of highly active antiretroviral therapy (HAART) drugs, zidovudine (3'-azido-3'-deoythymidine, AZT), 2',3'-dideoxy-3'-thiacytidine (3TC) and efavirenz (EFV). Thirty-six male SD rats were divided into three groups. Group A was given a combination of AZT, 3TC and EFV (AZT/3TC/EFV). Group B rats were given AZT/3TC/EFV simultaneously with SLFZC. Group C rats were given AZT/3TC/EFV 2h prior to SLFZC. Blood samples were collected at fixed time intervals. Plasma concentration of each antiretroviral drug was tested for calculation of pharmacokinetic parameters. There was significant difference among groups with respect to t1/2 for AZT (F=3.371, P<0.05), but the Student-Newman-Keuls (SNK) pairwise multiple comparison procedure showed no statistical differences in all pairwise comparisons (P>0.05). There were no significant differences among groups in terms of C max , T max , AUC 0-12h and CL for AZT, and t 1/2 , C max , T max , AUC 0-12h and CL for 3TC and EFV, respectively. The results indicate that SLFZC has little impact on pharmacokinetic properties of AZT, 3TC and EFV.

We previously verified a physiologically based pharmacokinetic (PBPK) model for mirabegron in healthy subjects using the Simcyp Simulator by incorporating data on the inhibitory effect on cytochrome P450 (CYP) 2D6 and a multi-elimination pathway mediated by CYP3A4, uridine 5'-diphosphate-glucuronosyltransferase (UGT) 2B7 and butyrylcholinesterase (BChE). The aim of this study was to use this PBPK model to assess the magnitude of drug-drug interactions (DDIs) in an elderly population with severe renal impairment (sRI), which has not been evaluated in clinical trials. We first determined the system parameters, and meta-analyses of literature data suggested that the abundance of UGT2B7 and the BChE activity in an elderly population with sRI was almost equivalent to and 20% lower than that in healthy young subjects, respectively. Other parameters, such as the CYP3A4 abundance, for an sRI population were used according to those built into the Simcyp Simulator. Second, we confirmed that the PBPK model reproduced the plasma concentration-time profile for mirabegron in an sRI population (simulated area under the plasma concentration-time curve (AUC) was within 1.5-times that of the observed value). Finally, we applied the PBPK model to simulate DDIs in an sRI population. The PBPK model predicted that the AUC for mirabegron with itraconazole (a CYP3A4 inhibitor) was 4.12-times that in healthy elderly subjects administered mirabegron alone, and predicted that the proportional change in AUC for desipramine (a CYP2D6 substrate) with mirabegron was greater than that in healthy subjects. In conclusion, the PBPK model was verified for the purpose of DDI assessment in an elderly population with sRI., (© 2019 John Wiley & Sons, Ltd.)

Clinical trials demonstrated intermittent preventive treatment in pregnancy with mefloquine (MQ) reduced malaria rates among pregnant women, yet an unexpected higher risk of mother-to-child transmission (MTCT) of HIV among HIV-positive women receiving MQ has also been observed. To determine if interactions between antiretroviral drugs (ARVs) and MQ could contribute to the increased MTCT observed in women receiving MQ, we performed a retrospective cross-sectional analysis of ARV plasma concentrations in peripheral blood (maternal plasma) and cord blood (cord plasma) collected at delivery from 186 mothers participating in a randomized clinical trial of MQ (n = 102) compared with placebo (n = 84) in Kenya. Plasma zidovudine (AZT), lamivudine (3TC), and nevirapine (NVP) concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. Although only 4% (7/186) reported not using these ARVs, AZT, 3TC, and NVP were all below the limit of detection in 44% of maternal plasma and 42% of cord plasma samples, and proportions were similar between the two study arms. Median concentrations of AZT and 3TC were not significantly lower in the MQ arm compared with the placebo arm for maternal plasma and cord plasma (p > .05). However, median NVP concentrations were significantly lower in the MQ study arm compared with the placebo study arm in both maternal plasma (1,597 ng/mL vs. 2,353 ng/mL, Mann-Whitney Rank Sum, p = .023) and cord plasma (2,038 ng/mL vs. 2,434 ng/mL, p = .048). Reduced NVP concentrations in maternal and cord plasma of women receiving MQ suggest MQ may affect NVP metabolism for both mother and infant. These results highlight the need to evaluate potential drug-drug interactions between candidate antimalarials and ARVs for use in pregnant women.

Double layered one-by-one imprinted hollow core-shells@ pencil graphite electrode was fabricated for sequential sensing of anti-HIV drugs. For this, two eccentric layers were developed on the surface of vinylated silica nanospheres to obtain double layered one-by-one imprinted solid core-shells. This yielded hollow core-shells on treatment with hydrofluoric acid. The modified hollow core-shells (single layered dual imprinted) evolved competitive diffusion of probe/analyte molecules. However, the corresponding double layered one-by-one imprinted hollow core-shells (outer layer imprinted with Zidovudine, and inner layer with Lamivudine) were found relatively better owing to their bilateral diffusions into molecular cavities, without any competition. The entire work is based on differential pulse anodic stripping voltammetry at double layered one-by-one imprinted hollow core-shells. This resulted in indirect detection of electro inactive targets with limits of detection as low as 0.91 and 0.12 (aqueous sample), 0.94 and 0.13 (blood serum), and 0.99 and 0.20 ng mL -1 (pharmaceutics) for lamivudine and zidovudine, respectively in anti-HIV drug combination., (Copyright © 2018 Elsevier B.V. All rights reserved.)

HIV infection is often associated with liver failure, which alters the pharmacokinetics of many drugs. In this study we investigated whether acute liver failure (ALF) altered the pharmacokinetics of the first-line anti-HIV agent zidovudine (AZT), a P-gp/BCRP substrate, in rats. ALF was induced in rats by injecting thioacetamide (TAA, 300 mg·kg -1 ·d -1 , ip) for 2 days. On the second day after the last injection of TAA, the pharmacokinetics of AZT was investigated following both oral (20 mg/kg) and intravenous (10 mg/kg) administration. ALF significantly increased the plasma concentrations of AZT after both oral and intravenous doses of AZT, but without affecting the urinary excretion of AZT. AZT metabolism was studied in rat hepatic microsomes in vitro, which revealed that hepatic UGT2B7 was the main enzyme responsible for the formation of AZT O-glucuronide (GAZT); ALF markedly impaired AZT metabolism in hepatic microsomes, which was associated with the significantly decreased hepatic UGT2B7 expression. Intestinal absorption of AZT was further studied in rats via in situ single-pass intestinal perfusion. Intestinal P-gp function and intestinal integrity were assessed with rhodamine 123 and FD-70, respectively. We found that ALF significantly downregulated intestinal P-gp expression, and had a smaller effect on intestinal BCRP. Further studies showed that ALF significantly increased the intestinal absorption of both rhodamine 123 and AZT without altering intestinal integrity, thus confirming an impairment of intestinal P-gp function. In conclusion, ALF significantly increases the oral plasma exposure of AZT in rats, a result partly attributed to the impaired function and expression of hepatic UGT2B7 and intestinal P-gp.

Objectives: Zidovudine (AZT) is mainly used to prevent mother-to-child HIV-1 transmission (PMTCT). Despite serious concerns on AZT-associated toxicity, there is little information on pharmacokinetics of intracellular AZT metabolites in infants., Methods: We conducted a prospective study in 31 HIV-uninfected infants who received AZT for PMTCT. Blood samples were obtained from 14 infants on postdelivery days (PDD) 1, 7, 14, and 28 and from 17 infants at 0 and 4 hours after dosing on PDD-1. Plasma AZT concentrations (pAZT) and intracellular concentrations of AZT-monophosphate (icAZT-MP), diphosphate (icAZT-DP), and triphosphate (icAZT-TP) were determined., Results: Plasma AZT and icAZT-MP concentrations were 2713 nmol/L and 79 fmol/10 cells in PDD-1, but decreased to 1437 nmol/L and 31 fmol/10 cells by PDD-28 (P = 0.02 and P = 0.07 for all PDDs, respectively), whereas those of icAZT-DP and icAZT-TP remained low throughout the sampling period (P = 0.29 and P = 0.61 for all PDDs, respectively) There were no differences in icAZT-TP between infants of the 2 mg/kg 4 times a day dose and 4 mg/kg twice daily dose (P = 0.25), whereas pAZT and icAZT-MP levels were higher in the latter (P < 0.01 and <0.01, respectively). The pAZT and icAZT-MP significantly increased from 0 to 4 hours after dosing (P < 0.001 and <0.001, respectively), whereas icAZT-DP, icAZT-TP levels were not changed (P = 0.41 and 0.33, respectively)., Conclusions: The level of icAZT-TP did not change with age, time, or a single dose despite the wide range of pAZT concentration. A safer dosage needs to be determined because high pAZT levels do not parallel those of icAZT-TP.

Although zidovudine (AZT) is not the preferred antiretroviral drug for adult HIV-infected patients, it is still widely used in infants for both prevention of mother-to-infant HIV-1 transmission and treatment of HIV-infected children. However, it is difficult to measure intracellular concentrations of AZT metabolites in small blood samples due to their extremely low concentrations in peripheral blood mononuclear cells and interference by endogenous nucleotide triphosphates, residual plasma phosphates and electrolytes. We developed an ultrasensitive assay using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for measurement of intracellular concentrations of zidovudine (AZT)-monophosphate (AZT-MP), -diphosphate (AZT-DP) and -triphosphate (AZT-TP). The high sensitivity was due to the improvement of peripheral blood mononuclear cells extraction for complete removal of plasma and electrolytes, alkalization of LC buffer and use of alkaline-stable high performance liquid chromatography column and tetrabutylammonium hydroxide as the ion pair. Using this method, the lower limits of quantification of AZT, AZT-MP, -DP and -TP were 6, 6, 10 and 10 fmol per sample, respectively. Accuracy ranged 89-115% and precision was lower than 15% in the quantification range of 6-6000 fmol/sample for plasma AZT and intracellular AZT-MP and 10-10 000 fmol/sample for AZT-DP and -TP. The validation parameters met the international requirements. Among nine AZT-treated HIV-infected adult patients, five had low AZT-TP levels (<10 fmol/10(6) cells). Our assay has high sensitivity and is advantageous for evaluation of AZT phosphates in children and infants based on minimum blood sampling requirement., (Copyright © 2015 John Wiley & Sons, Ltd.)

Pharmacokinetics of lamivudine (3TC)/zidovudine (ZDV) and lopinavir/ritonavir (LPV/r) are described in a gravid 27-year-old HIV-infected woman with gastric bypass. Blood levels were obtained for these medications at time points 0 (predose) and 1, 2, 4, 6, 8, and 12 hours postdose. For these times, the levels (µg/mL) of 3TC were 0.0801, 0.69, 0.339, 0.237, 0.202, 0.108, and 0.0461; the levels of ZDV were 0.0153, 0.433, 0.0717, 0.0481, 0.0107, 0.0214, and 0.00864; the levels of lopinavir (LPV) were 2.45, 2.64, 1.95, 2.78, 3.83, 3.20, and 1.92; and the levels of ritonavir (RTV) were 0.09, 0.10, 0.07, 0.11, 0.15, 0.15, and 0.06. These data suggest that gastric bypass affected these antiretroviral drug levels. A functional, intact small bowel is responsible for absorption of these medications., (© The Author(s) 2014.)

In this study, we aimed to determine the modulatory effects of warfarin (an extensively used anticoagulant drug) and its metabolites on UDP-glucuronosyltransferase (UGT) activity and to assess the potential of warfarin to alter the pharmacokinetics of zidovudine (AZT). The effects of warfarin and its metabolites on glucuronidation were determined using human and rat liver microsomes (HLM and RLM) as well as expressed UGTs. The mechanisms of warfarin-UGT interactions were explored through kinetic characterization and modeling. Pharmacokinetic studies with rats were performed to evaluate the potential of warfarin to alter the pharmacokinetics of AZT. We found that warfarin was an effective modifier of a panel of UGT enzymes. The effects of warfarin on glucuronidation were inhibitory for UGT1A1, 2B7, and 2B17, but activating for UGT1A3. Mixed effects were observed for UGT1A7 and 1A9. Consistent with its inhibitory effects on UGT2B7 activity, warfarin inhibited AZT glucuronidation in HLM (Ki = 74.9-96.3 μM) and RLM (Ki = 190-230 μM). Inhibition of AZT glucuronidation by UGT2B7, HLM, and RLM was also observed with several hydroxylated metabolites of warfarin. Moreover, the systemic exposure (AUC) of AZT in rats was increased by a 1.5- to 2.1-fold upon warfarin coadministration. The elevated AUC was associated with suppressed glucuronidation that was probably attained through a combined action of warfarin and its hydroxylated metabolites. In conclusion, the activities of multiple UGT enzymes can be modulated by warfarin and the nature of modulation was isoform dependent. Also, pharmacokinetic interactions of zidovudine with warfarin were highly possible through inhibition of UGT metabolism., (© 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.)

Background: Lopinavir/ritonavir (LPV/r) is available in a liquid formulation that is far from ideal for treatment of children in resource-poor settings. Flexible, low-cost, solid, oral fixed-dose combinations (FDC) of LPV/r with nucleoside reverse transcriptase inhibitors (LPV/r/abacavir [ABC]/lamivudine [3TC] and LPV/r/zidovudine [ZDV]/3TC) are needed to improve both management and adherence of children. This work aimed to develop appropriate drug ratios and dosing for each FDC., Methods: Data from 25 combined datasets included therapeutic drug monitoring and clinical studies from IMPAACT and PENTA. Population pharmacokinetic analyses were performed using Monolix. Monte-Carlo simulations of WHO and FDA dosing recommendations were performed to assess their ability to provide optimal exposure in children weighing 4 to 25 kg based on consensus plasma targets. The LPV/r:3TC:ZDV(ABC) dose ratios were 2.67:1:2(2), respectively., Results: Using WHO dosage, LPV efficacy target was reached in all weight bands. Given the recommended drug ratios, the dosage for the 4-5.9 kg weight band (LPV/ZDV: 120/90 mg twice daily [bid]) showed more than 20% of subjects had ZDV levels at high risk of neutropenia. Reducing the LPV/ZDV dose to 80/60 mg bid decreased frequency of high ZDV concentrations but retained the LPV efficacy criteria., Conclusions: This defined a flexible and simple FDC containing 40 mg LPV, 10 mg ritonavir, 15 mg 3TC and 30 mg ABC or ZDV. According to the weight bands defined by WHO, 4-5.9 kg, 6-9.9 kg, 10-13.9 kg, 14-19.9 kg, 20-24.9 kg, therapeutic doses would be 2, 3, 4, 5 or 6 individual units administered by oral route bid.

The zidovudine (ZDV) is the first drug approved for the treatment of HIV virus infection. The detection and determination of this drug are very importance in human serum because of its undesirable effects. A new ZDV sensor was fabricated on the basis of nanocomposite of silver nanofilm (Ag-NF) and multiwalled carbon nanotubes (MWCNTs) immobilized on glassy carbon electrode (GCE). The modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) techniques. Results showed that the electrodeposited silver has a nanofilm structure and further electrochemical studies showed that the prepared nanocomposite has high electrocatalytic activity and is appropriate for using in sensors. The amperometric technique under optimal conditions is used for the determination of ZDV ranging from 0.1 to 400ppm (0.37μM-1.5mM) with a low detection limit of 0.04ppm (0.15μM) (S/N=3) and good sensitivity. The prepared sensor possessed accurate and rapid response to ZDV and shows an average recovery of 98.6% in real samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The aims of this study were to describe the pharmacokinetics of zidovudine (ZDV) and its biotransformation to its metabolite, 3*-azido-3*-deoxy-5*-glucuronylthymidine (G-ZDV), in HIV-infected children, to identify factors that influence the pharmacokinetics of ZDV, and to compare and evaluate the doses recommended by the World Health Organization (WHO) and the Food and Drug Administration (FDA). ZDV concentrations in 782 samples and G-ZDV concentrations in 554 samples from 247 children ranging in age from 0.5 to 18 years were retrospectively measured. A population pharmacokinetic model was developed with NONMEM software (version 6.2), and the pharmacokinetics of ZDV were best described by a one-compartment model with first-order absorption and elimination. The effect of body weight on the apparent elimination clearance and volume of distribution was significant. The mean population parameter estimates were as follows: absorption rate, 2.86 h(-1); apparent elimination clearance, 89.7 liters · h(-1) (between-subject variability, 0.701 liters · h(-1)); apparent volume of distribution, 229 liters (between-subject variability, 0.807 liters); metabolic formation rate constant, 12.6 h(-1) (between-subject variability, 0.352 h(-1)); and elimination rate constant of G-ZDV, 2.27 h(-1). On the basis of simulations with FDA and WHO dosing recommendations, the probabilities of observing efficient exposures (doses resulting in exposures of between 3 and 5 mg/liter · h) with less adverse events (doses resulting in exposures below 8.4 mg/liter · h) were higher when the FDA recommendations than when the WHO recommendations were followed. In order to improve the FDA recommendations, ZDV doses should be reconsidered for the weight band (WB) of 20 to 40 kg. The most appropriate doses should be decreased from 9 to 8 mg/kg of body weight twice a day (BID) for the WB from 20 to 29.9 kg and from 300 to 250 mg BID for the WB from 30 to 39.9 kg. The highest dose, 300 mg BID, should be started from body weights of 40 kg.

A simple, rapid, and sensitive high performance liquid chromatographic method with UV detection has been developed and validated according to the FDA guidelines for the quantitation of zidovudine (ZDV), lamivudine (LMV), and nevirapine (NVR) in human plasma. The sample was prepared by simple liquid-liquid extraction. Chromatographic separation was carried out in a Hypersil BDS, C(18) column (250 mm × 4.6 mm; 5 µm particle size) with simple mobile phase composition of 0.1 M ammonium acetate buffer in 0.5% acetic acid, v/v and methanol (40:60, v/v) at a flow rate of 0.85 ml min(-1) where detector was set at 270 nm with a total run time of 10 min which is very short for simultaneous estimation of three analytes in plasma. The method was linear over the concentration range of 50-3000, 50-2000 and 10-3000 ng ml(-1) with lower limit of quantifications (LLOQ) of 50, 50, and 10 ng ml(-1) for ZDV, LMV, and NVR, respectively. Accuracy and precision values of both within-run and between-run obtained from six different sets of three quality control (QC) samples along with the LLOQ analyzed in separate occasions for all the analytes ranged from 94.47-99.71% and 0.298-3.507%, respectively. Extraction recovery of analytes in plasma samples was above 90.16%. In stability tests, all the analytes in human plasma were stable during storage and assay procedure. The developed and validated method was successfully applied to quantitative determination of the three analytes in plasma for pharmacokinetic study in 12 healthy human volunteers., (Copyright © 2012 John Wiley & Sons, Ltd.)

A selective and sensitive high performance liquid chromatography-tandem mass spectrometry method has been developed and validated for simultaneous determination of zidovudine (ZDV), lamivudine (3TC) and nevirapine (NVP) in human plasma. After Solid phase extraction (SPE), analytes and ISTDs were run on Peerless Basic C18 column with an injection volume of 3μL and run time of 3.0min. An isocratic mobile phase of 0.1% formic acid in water:methanol (15:85, v/v) was used with positive mass spectrometric detection. The method was validated over a concentration range of 5-1500ng/mL for ZDV and 3TC and over the concentration range of 10-3000ng/mL for NVP. The intraday and interday precision and accuracy across four validation runs were ranged from 1.6 to 10.1% and 93.8 to 110.8% respectively., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Objective: Phase 0 studies can provide initial pharmacokinetics (PKs) data in humans and help to facilitate early drug development, but their predictive value for standard dosing is controversial. To evaluate the prediction of microdosing for active intracellular drug metabolites, we compared the PK profile of 2 antiretroviral drugs, zidovudine (ZDV) and tenofovir (TFV), in microdose and standard dosing regimens., Study Design: We administered a microdose (100 μg) of C-labeled drug (ZDV or tenofovir disoproxil fumarate) with or without a standard unlabelled dose (300 mg) to healthy volunteers. Both the parent drug in plasma and the active metabolite, ZDV-triphosphate (ZDV-TP) or TFV-diphosphate (TFV-DP) in peripheral blood mononuclear cells (PBMCs) and CD4 cells were measured by accelerator mass spectrometry., Results: The intracellular ZDV-TP concentration increased less than proportionally over the dose range studied (100 μg-300 mg), whereas the intracellular TFV-DP PKs were linear over the same dose range. ZDV-TP concentrations were lower in CD4 cells versus total PBMCs, whereas TFV-DP concentrations were not different in CD4 cells and PBMCs., Conclusions: Our data were consistent with a rate-limiting step in the intracellular phosphorylation of ZDV but not TFV. Accelerator mass spectrometry shows promise for predicting the PK of active intracellular metabolites of nucleosides, but nonlinearity of PK may be seen with some drugs.

A methodology based on micellar liquid chromatography to monitor five antiretroviral drugs (lamivudine, stavudine, tenofovir, zidovudine and efavirenz) was proposed. Antiretrovirals were studied in sets of three, corresponding to each highly active antiretroviral therapy (HAART) regime, prescribed to acquired immunodeficiency syndrome (AIDS)-infected patients. Four aqueous micellar mobile phases buffered at pH 7 were optimized to separate these compounds, using sodium dodecyl sulfate as the tensioactive, and 1-propanol or 1-pentanol as the organic modifier. The composition of each mobile phase was optimized for each antiretroviral. The common separation conditions were: C18 apolar column (125 × 4.6 mm, 5 μm particle size), UV detection set at 214 nm, and mobile phase running at 1 mL min(-1) without controlling the temperature. The finally suggested method was validated for five analysed antiretroviral drugs following the US Food and Drug Administration guidelines in terms of: linearity between 0.5 and 50 ppm (r(2) > 0.9995), sensitivity (LOD lower than 0.25 ppm), intra- and inter-day precision (<7.1 and <5.2%, respectively) and accuracy (recovery 88.5-105.3% and 93.5-101.3%, respectively), as well as robustness (<6.5%). The proposed method was used to monitor the level of antiretrovirals in the serum of AIDS patients. The suggested methodology was found to be useful in the routine analysis of antiretrovirals in serum samples.

The nucleoside reverse transcriptase inhibitors lamivudine and zidovudine and the protease inhibitors lopinavir and ritonavir are currently used in anti-human immunodeficiency virus (HIV) therapy. Here, a high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) method, using a hybrid quadrupole time-of-flight mass analyzer, is reported for the simultaneous quantification of lamivudine, lopinavir, ritonavir, and zidovudine in plasma of HIV-infected patients. The volume of plasma sample was 600 μL. Plasma samples were extracted by solid-phase using 1 cc Oasis HLB Cartridge (divinylbenzene and N-vinylpyrrolidone) and evaporated in a water bath under nitrogen stream. The extracted samples were reconstituted with 100-μL methanol. Five microliters of the reconstituted samples were injected into a HPLC-MS/MS apparatus, and the analytes were eluted on a Vydac column (250 × 1.0 mm i.d.) filled with 3-μm C(18) particles. The mobile phase was delivered at 70 μL/min with a linear gradient elution, both acetonitrile and ultrapure water solvents contained 0.2% formic acid. The calibration curves were linear from 0.47 to 20 ng/mL. The absolute recovery ranged between 91 and 107%. The minimal concentration of lamivudine, lopinavir, ritonavir, and zidovudine detectable by HPLC-MS/MS is 0.47, 0.28, 0.30, and 0.66 ng/mL, respectively. The great advantage of the new HPLC-MS/MS method here reported is the possibility to achieve a very high specificity toward the selected anti-HIV drugs, despite the simple and rapid sample preparation. Moreover, this method is easily extendible to the analysis of co-administrated drugs., (Copyright © 2012 Wiley Periodicals, Inc.)

A sensitive LC/MS/MS assay for determining zidovudine (ZDV) and lamivudine (3TC) in human plasma was validated to support antiretroviral pharmacology research programs. After addition of stable labeled isotopic zidovudine (ZDV-IS) and lamivudine (3TC-IS) as internal standard, a solid-phase extraction was performed with an Oasis HLB 1 cm(3) cartridge, with recoveries of 92.3% for ZDV and 93.9% for 3TC. A Phenomonex Synergi Hydro-RP (2.0 ×150 mm) reversed-phase analytical column was utilized for chromatographic separation. The mobile phase consisted of an aqueous solution of 15% acetonitrile and 0.1% acetic acid. Detection was accomplished by ESI/MS/MS in the positive ion mode, monitoring 268/127, 271/130, 230/112 and 233/115 transitions, for ZDV, ZDV-IS, 3TC and 3TC-IS, respectively. The method was linear from 1 to 3000 ng/mL with a minimum quantifiable limit of 1 ng/mL when 100 μL of plasma was analyzed. Validation results demonstrated high accuracy (≤8.3% deviation) and high precision (≤10% CV) for the quality control samples. The method was also shown to be specific and reproducible. The value of the high sensitivity was demonstrated by quantitation of approximately 100 existing samples that had ZDV below the limit of quantitation using a previously validated, less sensitive HPLC-UV method utilized in the laboratory., (Copyright © 2011 John Wiley & Sons, Ltd.)

The aim of this study was to develop and evaluate a Zidovudine (AZT)-loaded microparticulated bioadhesive vaginal gel (MBVG) in order to obtain a controlled releasing, safe gel delivery system. AZT microparticles (ZMPs) were evaluated for encapsulation efficiency, drug loading, surface morphology and in vitro drug release profiles and drug release mechanism and optimized. The optimized ZMPs were then encompassed in bioadhesive gel using different bioadhesive polymers and evaluated for the drug encapsulation efficiency, drug loading, in vitro and in vivo drug release profiles, drug release mechanism and vaginal irritancy study. From the dissolution data of ZMP4 and MBVG4 showed a zero-order diffusion pattern and Fickian diffusion case I transport mechanism in 24 and 36 h, respectively. On the basis of a pharmacokinetic study of MBVG4 (containing ZMP: Carbopol 1:4), it was found to have better bioavailability, larger AUC and T(max) in comparison to an oral pure suspension of AZT.

Nucleoside reverse transcriptase inhibitors (NRTIs) are a key class of drugs for the treatment of HIV infection. NRTIs are intracellularly phosphorylated to their active triphosphate metabolites and compete with endogenous deoxynucleotides (dNTP) for substrate binding. It is therefore important to analyze the intracellular concentrations of these compounds to understand drug efficacy and toxicity. To that purpose an analytical platform was developed that is capable of analyzing 8 NRTIs, 12 phosphorylated NRTIs and 4 dNTPs in small numbers of peripheral blood mononuclear cells, i.e. 1 × 10(6) cells. The platform consists of two liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods: a reversed-phase method for NRTIs using positive electrospray ionization (ESI) and an ion-pair LC-MS/MS method for the phosphorylated compounds using negative ESI. The methods use the same LC-MS system and column and changing from one method to the other only includes changing the mobile phase. The methods were partially validated, focussing on sensitivity, accuracy and precision. Successful transfer of the methods to ultra performance liquid chromatography (UPLC) led to a significant improvement of speed for the analysis of NRTIs and sensitivity for both NRTIs and phosphorylated NRTIs. The latter was demonstrated by the improved separation by UHPLC of dGTP vs. AZT-TP and ATP which made direct analysis of dGTP possible using the optimal MS/MS transition thereby significantly improving the detection limit of dGTP. Typically LLOQs observed for both the NRTIs and phosphorylated NRTIs were 1 nM, while the mean accuracy varied between 82 and 120% and inter- and intra-assay precision was generally <20%., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The purpose of this study was to investigate the olfactory transfer of zidovudine (ZDV) after intranasal (IN) administration and to assess the effect of thermoreversible gelling system on its absorption and brain uptake. The nasal formulation was prepared by dissolving ZDV in pH 5.5 phosphate buffer solution comprising of 20% polyethylene oxide/propylene oxide (Poloxamer 407, PLX) as thermoreversible gelling agent and 0.1% n-tridecyl-β-D-maltoside (TDM) as permeation enhancer. This formulation exhibited a sufficient stability and an optimum gelation profile at 27-30 °C. The in vitro permeation studies across the freshly excised rabbit nasal mucosa showed a 53% increase in the permeability of ZDV from the formulation. For in vivo evaluation, the drug concentrations in the plasma, cerebrospinal fluid (CSF) and six different regions of the brain tissues, i.e. olfactory bulb (OB), olfactory tract (OT), anterior, middle and posterior segments of cerebrum (CB), and cerebellum (CL) were determined by LC/MS method following IV and IN administration in rabbits at a dose of 1mg/kg. The IN administration of Poloxamer 407 and TDM based formulation showed a systemic bioavailability of 29.4% while exhibiting a 4 times slower absorption process (t(max) = 20 min) than control solution (t(max) = 5 min). The CSF and brain ZDV levels achieved after IN administration of the gelling formulation were approximately 4.7-56 times greater than those attained after IV injection. The pharmacokinetic and brain distribution studies revealed that a polar antiviral compound, ZDV could preferentially transfer into the CSF and brain tissue via an alternative pathway, possibly olfactory route after intranasal administration., (Copyright © 2011. Published by Elsevier B.V.)

This study focused on determining the concentration of zidovudine (AZT) and polystyrene sulfonate (PSS) in the plasma and vaginal tissue of the large white pig from an intravaginal bioadhesive polymeric device (IBPD). Biocompatible polymers were compressed with AZT and PSS into caplet-shaped devices for insertion into the posterior fornix of the pig vagina. A total of 25 pigs were used in this study. Plasma was sampled from the jugular vein at various time points after insertion of the IBPD reaching 28 days. At day 28, the pigs were euthanized and vaginal tissue was removed and digested with subtilisin for AZT and PSS extraction. The mean concentration detected in vaginal tissue at day 28 was 1.214 ± 0.062 mg/mL for AZT and 1.400 ± 0.071 mg/mL for PSS. Plasma concentration was significantly lower for AZT (0.332 ± 0.014 mg/mL) and PSS (0.256 ± 0.013 mg/mL). This indicated higher retention of AZT and PSS within the vaginal tissue. Molecular mechanics simulations blueprinted polymer-drug-mucin force-field interactions and energies that explicated the spatial preference of AZT and PSS for the vaginal tissue. Histopathotoxicity studies revealed negative-to-mild foreign body events and results strongly suggest that the IBPD may be suitable for prolonged intravaginal drug delivery in preventing the transmission of sexually transmitted infections and HIV/AIDS., (Copyright © 2010 Wiley-Liss, Inc.)

Background: Alternatives to the available stavudine-containing paediatric fixed-dose combination (FDC) tablets are rapidly needed due to concerns regarding the cumulative toxicity of long-term stavudine exposure. We report the bioavailability and short-term safety of a novel paediatric FDC tablet of zidovudine (ZDV)/lamivudine (3TC)/nevirapine (NVP; 30/15/28 mg) in HIV-infected children., Methods: In this Phase I/II open-label pharmacokinetic study, 42 children weighing 6-30 kg treated with NVP-based HAART for ≥4 weeks were randomized to receive the FDC tablets (GPO-VIR Z30) or the liquid formulations. Dosing was weight-based. Intensive 12-h blood sampling was performed after 2 weeks; subjects then crossed-over to the alternate formulation at equal doses and sampling repeated 2 weeks later. Pharmacokinetic parameters were determined by non-compartmental analysis. Buccal-swab samples were collected for cytochrome P450 (CYP)2B6 polymorphism analysis., Results: With the FDC tablet, the geometric mean (90% CI) area under the curve (AUC) for ZDV, 3TC and NVP was 1.58 (1.49-1.68), 7.78 (7.38-8.19) and 68.88 (62.13-76.36) μg•h/ml, respectively. Rules for NVP therapeutic inadequacy were defined a priori, and despite lower NVP exposure with the tablet (P<0.001), the levels remained therapeutically adequate. ZDV AUC was similar between formulations. 3TC exposure was significantly higher with the tablet but comparable to historical data in adults and children taking branded tablets. While receiving the tablet, NVP AUC in children with CYP2B 516 GG (45%), GT (45%) and TT (10%) genotypes were 67.0, 74.5 and 106.4 μg•h/ml, respectively (P=0.04)., Conclusions: Disparities in drug exposure between formulations were observed; however, the FDC tablet delivered therapeutically adequate exposures of each drug and could well play an important role in simplifying antiretroviral treatment for children.

Combination therapy with interferon-α and zidovudine (IFN/AZT) has been regarded as standard care for acute and indolent (i.e., chronic and smouldering) ATL based on reports involving a limited number of patients. This treatment approach has not been evaluated in Japan, a major endemic area of this disease in the world. This is the first Japanese report of IFN/AZT for ATL. It is impossible to draw any definitive conclusion from this small study; however, IFN/AZT showed clear anti-ATL effects for refractory/relapsed ATL patients. This report would contribute for developing future ATL treatment in Japan.

Accelerator mass spectrometry (AMS) is an ultrasensitive technique to detect radiolabeled compounds. We administered a microdose (100 µg) of (14)C-labeled zidovudine (ZDV) with or without a standard unlabeled dose (300 mg) to healthy volunteers. Intracellular ZDV-triphosphate (ZDV-TP) concentration was measured using AMS and liquid chromatography-tandem mass spectrometry (LC/MS/MS). AMS analysis yielded excellent concordance with LC/MS/MS and was 30,000-fold more sensitive. The kinetics of intracellular ZDV-TP formation changed several-fold over the dose range studied (100 µg-300 mg). AMS holds promise as a tool for quantifying intracellular drug metabolites and other biomediators in vivo.

Combination therapy with acyclovir and zidovudine is used for the treatment of herpes-infected immunocompromised patients. In the view of the optimal drug concentrations (minimum effective concentrations) for viral suppression and avoidance of drug toxicity, monitoring of drug levels has been considered essential to determine drug concentrations in plasma after administration of a dose of acyclovir and zidovudine. A simple, precise, and rapid RP-HPLC method has been developed for this purpose. Chromatographic separation was performed using methanol-water (50 + 50, v/v), pH 2.5 adjusted with orthophosphoric acid, as an isocratic mobile phase at a flow rate of 0.8 mL/min with an Inertsil ODS (C18) column (5 microm particle size, 250 x 4.60 mm id). Detection was carried out using a UV photo diode array detector at 258 nm. The plasma samples were prepared by a protein precipitation method. The retention time for acyclovir and zidovudine was 3.5 +/- 0.2 and 6.2 +/- 0.3 min, respectively. The method was linear in the range of 200-1800 and 400-3600 ng/mL with LOQ of 200 ng (SD = +/-1.4) and 400 ng (SD = +/-0.9) for zidovudine and acyclovir, respectively, in plasma. The mean accuracy was 98.0 and 96.4%, with average extraction recovery of 64.8 +/- 2.1 and 77.5 +/- 1.7% for lower nominal concentrations of acyclovir and zidovudine, respectively.

This study describes the preparation and evaluation of biodegradable poly(l-lactide) (PLA) and poly(l-lactide)-poly(ethylene glycol) (PLA-PEG) blend nanoparticles containing zidovudine as model drug. The prepared nanoparticles were characterized in terms of size, zeta potential, morphology and drug entrapment efficiency. The pharmacokinetics of zidovudine following intranasal administration in mice was assessed. The results showed that although PLA and blend nanoparticles had the same morphology, the particle size and zeta potential were changed by the PEG. The drug entrapment efficiency was increased by PEG presence. The pharmacokinetic study showed that all the nanoparticles were able to sustain zidovudine delivery over time, but greater efficiency was obtained with PLA-PEG blend nanoparticles, whose T(max) was twice that of PLA nanoparticles. The PLA and PLA-PEG nanoparticles formulations increased the zidovudine mean half-life by approximately 5.5 and 7h, respectively, compared to zidovudine aqueous solution. The relative bioavailability of zidovudine-loaded PLA-PEG blend nanoparticles was 2.7, relative to zidovudine-loaded PLA nanoparticles and 1.3 relative to aqueous solution formulation. Thus, the PLA nanoparticles were unable to increase the zidovudine bioavailability compared to aqueous solution formulation. The results obtained in this study indicate the potential of the PLA-PEG blend nanoparticles as carriers for zidovudine delivery by the intranasal route., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)

The purpose of this study was to evaluate the postmarket pharmaceutical equivalence, stability and bioequivalence of generic and innovator fixed dose combination products of lamivudine (3TC) and zidovudine (AZT) 150/300 mg tablets available in Nigeria. An isocratic HPLC-UV method was developed and validated for the quantitative determination of 3TC and AZT in human plasma and pharmaceutical samples. The model independent f(2) similarity factor was used to compare the dissolution profiles of the two products stored at accelerated and long-term stability conditions for 6 months. The f(2) values for 3TC and AZT in both products were found to be greater than 51. Also, the tablets were stable according to the USP potency and drug dissolution criteria with more than 80% of drug dissolution in 30 min indicating the pharmaceutical equivalence of the two products. The 90% confidence interval for the ratios of generic/innovator pharmacokinetic parameters for 3TC/AZT were 73.5-112.6/63.4-95.8 (C(max)); 68.5-105.6/68.0-114.8 (AUC(0-t)); and 64.2-106.2/80.1-120.3 (AUC(0-infinity)) respectively. The pharmacokinetic parameters failed to fully demonstrate bioequivalence between the products. The results underscored the importance of assessing the quality of the combination drug products that would ensure the safety and efficacy of the generic drug products available in the market., ((c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association)

A high performance liquid chromatographic method with UV detection was developed and validated for simultaneous determination of stavudine and lamivudine in human plasma using solid-phase extraction for sample clean-up. Zidovudine was used as an internal standard. Separation was performed on a C18 column by gradient elution with a mobile phase of 10 mM acetate buffer pH 6.5 and acetonitrile. The UV detection was set at 265 nm. The method proved to be specific, accurate, precise and linear over the concentration ranges of 50-3000 ng/ml for stavudine and 50-5000 ng/ml for lamivudine with correlation coefficients always > 0.996 for both drugs. The intra-day and inter-day precision and accuracy were less than 9.2% for both analytes. The absolute recoveries of both compounds ranged from 93.3 to 97.5%. The method was successfully applied to a bioavailability study of a combined tablet formulation containing 30 mg of stavudine and 150 mg of lamivudine compared with each reference formulation concurrently administered in 26 healthy Thai male volunteers.

Triphosphates anabolites are the active chemical species of nucleosidic reverse transcriptase inhibitors in HIV-therapy. Herein, we describe (i) the design of stable triphosphate analogues of AZT using molecular modelling, (ii) their synthesis and (iii) their use for producing anti AZT-TP antibodies in the aim of developing an immunoassay for therapeutic drug monitoring., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

A bioanalytical method for determination of lamivudine (3TC), zidovudine (AZT), and nevirapine (NVP) in 100 microL capillary blood applied onto sampling paper has been developed and validated. The antiretroviral drugs (ARV) were analyzed by reversed phase gradient liquid chromatography with UV detection. Separation was performed on a Zorbax SB C(8) (250 x 4.6 mm) column with a two-step gradient: (i) methanol-0.05 mol/L acetic acid-sodium acetate buffer (pH 3.95, 15:85 v/v) and (ii) methanol-0.05 mol/L acetic acid-sodium acetate buffer (pH 3.95, 50:50 v/v) with a flow rate of 1.0 mL/min. UV detection was performed at 260 nm. Total assay precisions were 6.3, 4.7, and 4.9% for 3TC at 0.34, 0.69, and 3.9 microg/mL, and 5.1, 5.5, and 3.2% for AZT at 0.40, 0.80, and 4.5 microg/mL. For NVP, total assay precisions were 5.2, 8.3, and 3.5% at 2.6, 4.5, and 8.8 microg/mL. Lower limit of quantifications (LLOQ) were 0.11 and 0.13 microg/mL for 3TC and AZT where the precisions were 2.0% for both the analytes. For NVP, LLOQ was 1.3 microg/mL where precision was 2.6%. Concentrations were determined for 10 h for two subjects receiving standard twice daily antiretroviral therapy containing 3TC, AZT, and NVP. Maximum 3TC concentrations were 2.5 and 2.8 microg/mL for subject 1 and 2, respectively. For AZT, maximum concentrations were 1.8 and 1.1 microg/mL while being 15 and 9.6 microg/mL for NVP. Pre-dose trough concentration of NVP was 11 microg/mL for subject 1 and 9.6 microg/mL for subject 2.

A sensitive method was developed and validated for simultaneous measurement of an investigational antiviral nucleoside, Amdoxovir (DAPD), its deaminated metabolite 9-(beta-D-1,3-dioxolan-4-yl)guanine (DXG), and Zidovudine (ZDV) in human plasma. This method employed high-performance liquid chromatography-tandem mass spectrometry with electrospray ionization. DXG and DAPD separation with sufficient resolution was necessary since they differ in only one mass to charge ratio, which increases the risk of overlapping MS/MS signals. However, the new method was observed to have functional sensitivity and specificity without interference. Samples were purified by ultrafiltration after protein precipitation with methanol. The total run time was 29 min. A linear calibration range from 2 to 3000 ng mL(-1) and 2 to 5000 ng mL(-1) was achieved for DAPD and DXG, and ZDV, respectively. Precisions and accuracies were both +/-15% (+/-20% for the lower limit of quantification) and recoveries were higher than 90%. Matrix effects/ion suppressions were also investigated. The analytes were chemically stable under all relevant conditions and the method was successfully applied for the analysis of plasma samples from HIV-infected persons treated with combinations of DAPD and ZDV.

Background: Lipoatrophy is known to be associated with stavudine as part of the treatment for HIV infection, but it is less clear if this serious side effect is also related to other nucleoside reverse transcriptase inhibitors like zidovudine. We aimed to determine whether zidovudine-sparing first-line antiretroviral therapy would lead to less lipoatrophy and other metabolic changes than zidovudine-containing therapy., Methodology/principal Findings: Fifty antiretroviral therapy-naïve HIV-1 infected men with an indication to start antiretroviral therapy were included in a randomized single blinded clinical trial. Randomisation was between zidovudine-containing therapy (zidovudine/lamivudine+lopinavir/ritonavir) and zidovudine-sparing therapy (nevirapine+lopinavir/ritonavir). Main outcome measures were body composition assessed by computed tomography and dual-energy X-ray absorptiometry scan and lipid profile before and after 3, 12, 24 months of antiretroviral therapy. In the zidovudine/lamivudine+lopinavir/ritonavir group, from 3 months onward limb fat decreased progressively by 684+/-293 grams (estimated mean+/-standard error of the mean)(p = 0.02) up to 24 months whereas abdominal fat increased, but exclusively in the visceral compartment (+21.9+/-8.1 cm(2), p = 0.008)). In contrast, in the nevirapine+lopinavir/ritonavir group, a generalized increase in fat mass was observed. After 24 months no significant differences in high density lipoprotein and total/high density lipoprotein cholesterol ratio were found between both treatment groups, but total and low density lipoprotein cholesterol levels were higher in the nevirapine+lopinavir/ritonavir group (6.1+/-0.2 versus 5.3+/-0.2 and 3.6+/-0.1 versus 2.8+/-0.1 mmol/l respectively, p<0.05). Virologic response and safety were comparable in both groups., Conclusions/significance: Zidovudine/lamivudine+lopinavir/ritonavir, but not nevirapine+lopinavir/ritonavir in antiretroviral therapy-naïve patients, is associated with lipoatrophy and greater relative intraabdominal lipohypertrophy, suggesting that zidovudine/lamivudine contributes to both these features of lipodystrophy. These findings support to no longer consider zidovudine/lamivudine as one of the preferred possible components of first-line antiretroviral therapy where alternative treatments are available., Trial Registration: ClinicalTrials.gov NCT 00122226.

A molecularly imprinted polymer (MIP) using zidovudine (AZT) as template and methacrylic acid as monomer was prepared. The synthesis of the MIP was performed in acetonitrile. The synthesized material was then tested for the solid-phase extraction of AZT from different media (pure organic solvents and hydro-organic mixtures). An optimised procedure was developed for the selective extraction of AZT with a recovery of 96% using the MIP and only 3% on a non-imprinted polymer used as control polymer. A specific capacity of 0.2 micromol g(-1) was determined. The specificity of the MIP was evaluated by studying the retention behaviour of two others nucleoside analogues. The feasibility of the MIP to selectively extract AZT and stavudine (d4T) from human serum was also demonstrated with recoveries of 80 and 85% respectively. The lower limit of quantification (LLOQ) and the lower limits of detection (LLOD) for AZT were 5.10(-7) and 10(-7) M respectively.

The new non-reversed transcriptase inhibitor (NRTI) drugs for treatment of acquired immunodeficiency syndrome (AIDS) are reported. An improvement in the sensitivity and selectivity of high-performance liquid chromatography was obtained by diamond electrode-electrochemical detector and fluorescence detector owing to different structural information. The four anti-retroviral NRTI drugs (abacavir, didanosine, lamivudine and zidovudine) were separated on a CapcellPak C18 UG120 column (250 mm x 4.6 mm I.D., 5 microm) with an acetonitrile-25 mM potassium dihydrogenphosphate buffer (pH 8.0; 1:9, v/v) as the mobile phase. We applied dual detection (electrochemical detection and florescence detection) for improving the peak identification and also for improved selectivity, which assisted monitoring by trace-volume samples (e.g., plasma). The electrochemical detector, equipped with a diamond electrode, was set at 2000 mV (applied voltage) and the fluorescence detector was set at excitation wavelength 275 nm and emission wavelength 315 nm. The detection limits of the four NRTIs in spiked plasma were 1-100 ng/ml by electrochemical detection and 5-10 pg/ml by fluorescence detection. The calibration graphs were linear up to 20 microg/ml by electrochemical detection and 10 microg/ml by fluorescence detection. This is the first report of LC analysis of NRTIs by electrochemical detection, also combined with fluorescence detection. The detection limits of didanosine, lamivudine and zidovudine were improved 20-fold by electrochemical detection and 500-fold by fluorescence detection compared to previous reports on UV detection. The selectivity was also improved by dual detection. The proposed method was applied to the preliminary monitoring of NRTIs in plasma.

There are limited data describing the concentrations of zidovudine, lamivudine, and nevirapine in nursing infants as a result of transfer via breast milk. The Kisumu Breastfeeding Study is a phase IIb open-label trial of prenatal, intrapartum, and postpartum maternal treatment with zidovudine, lamivudine, and nevirapine from 34 weeks of gestation to 6 months postpartum. In a pharmacokinetic substudy, maternal plasma, breast milk, and infant dried blood spots were collected for drug assay on the day of delivery and at 2, 6, 14, and 24 weeks after delivery. Sixty-seven mother-infant pairs were enrolled. The median concentrations in breast milk of zidovudine, lamivudine, and nevirapine during the study period were 14 ng/ml, 1,214 ng/ml, and 4,546 ng/ml, respectively. Zidovudine was not detectable in any infant plasma samples obtained after the day of delivery, while the median concentrations in infant plasma samples from postpartum weeks 2, 6, and 14 were 67 ng/ml, 32 ng/ml, and 24 ng/ml for lamivudine and 987 ng/ml, 1,032 ng/ml, and 734 ng/ml for nevirapine, respectively. Therefore, lamivudine and nevirapine, but not zidovudine, are transferred to infants via breast milk in biologically significant concentrations. The extent and effect of infant drug exposure via breast milk must be well understood in order to evaluate the benefits and risks of maternal antiretroviral use during lactation.

Objective: To evaluate the efficacy of postexposure prophylaxis with a combination of zidovudine (ZDV), lamivudine (3TC) and indinavir (IDV), after vaginal exposure to HIV., Design: : Experimental intravaginal exposure of female cynomolgus macaques to SIVmac251., Methods: ZDV/3TC/IDV treatment was initiated 4 h after exposure and continued for 28 days. Groups of six animals received a placebo or a combination of oral ZDV (4.5 mg/kg), 3TC (2.5 mg/kg) and IDV (20 mg/kg) twice daily or subcutaneous ZDV (4.5 mg/kg) and 3TC (2.5 mg/kg) twice daily, and a higher dose of IDV (60 mg/kg) administered orally twice daily., Results: In the placebo group, all animals were infected. Antiretroviral association protected one of the six animals if all drugs were administered orally and four of the six animals if ZDV and 3TC were administered subcutaneously and IDV was given orally at triple dose. In infected animals, viremia was significantly delayed and lowered in treated animals than in animals given placebo, and high CD4 cell counts were maintained in the treated animals, at least in the medium term. Antiretroviral dosages made in macaques receiving the same treatments showed that protection efficacy could be linked to antiretroviral plasmatic concentration., Conclusion: This study shows, for the first time in macaques, that the postexposure prophylaxis recommended for humans may be effective after vaginal exposure. Improvements in pharmacokinetic parameters significantly increased treatment efficiency.

The development and validation of a simple and accurate method based on HPLC with ultraviolet detection for the quantification of zidovudine in rat plasma and its application to a pharmacokinetic study following a single intranasal dose zidovudine is described. Zidovudine was extracted from the plasma using a single-step deproteinization. Chromatographic separation of zidovudine from interfering components was achieved with a C-18 reverse phase column, a mobile phase consisting of a mixture of sodium acetate buffer (55 mM) with pH adjusted to 7.0 and acetonitrile (91:9 v/v) and UV detection set at 265 nm. The method was linear from 100 to 10,000 ng.mL(-1) (r(2) > or = 0.9995), and zidovudine had a mean recovery from plasma of 92.8%. The coefficient of variation of inter-day and intra-day quality control samples was less than 15%. After a single intranasal dose of zidovudine administered to rats, pharmacokinetic parameters (AUC(0-24), C(max), t(max), t(1/2)) were determined. The proposed method was found to be simple, specific, accurate, and precise and could be applied to the quantitative analysis of clinical pharmacokinetic studies of zidovudine in rats.

Purpose: The objective of this study was to examine lamivudine (3TC), zidovudine (ZDV), nelfinavir (NFV), and its active nelfinavir metabolite (M8) concentrations in paired maternal plasma and amniotic fluid samples to determine antiretroviral penetration or accumulation in the fetal compartment., Method: Ten paired amniotic fluid and maternal plasma samples were obtained during caesarian section for pharmacokinetic analysis. Antiretroviral concentrations were measured in both matrices using high-performance liquid chromatography (HPLC) and mass spectrometry (LC/MS) methodologies., Results: Median maternal plasma concentrations for NFV, M8, 3TC, and ZDV were 456, 244, 176, and 794 ng/mL, respectively, while median amniotic fluid concentrations were 118, 21, 2537, and 1483 ng/mL, respectively. The median NFV amniotic fluid to maternal plasma ratio was 0.44; the median M8 ratio was 0.11. Median 3TC and ZDV amniotic fluid to plasma ratios were 11.9 and 1.5, respectively., Conclusions: NFV and M8 exhibited partial drug transfer and/or accumulation in the amniotic compartment, whereas ZDV and 3TC concentrations mostly exceeded that in maternal plasma. Overall, all drugs achieved exposures in the amniotic fluid in excess of their wild-type viral susceptibilities. Amniotic fluid is an important compartment in the prevention of mother-to-child transmission; a further understanding of protease inhibitor and other antiretroviral drug penetration into amniotic fluid is warranted.

A rapid, simple, and sensitive high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) method was developed and validated for quantitative analysis of 3'-azido-3'-deoxythymidine (zidovudine, AZT) diaryl phosphate triester pro-drugs, in rat plasma using 2',3'-dideoxy-2'3'-didehydrothymidine (d4T) as internal standard (IS). The analytes were extracted from rat plasma with methanol after protein precipitation. The compounds were separated by HPLC with gradient elution (on a Shim-pack VP-ODS C(18) analytical column using a mobile phase of methanol/10mM ammonium acetate). All the analytes were detected in positive ion mode using multiple reaction monitoring (MRM). The method was validated and the specificity, linearity, lower limit of quantitation (LLOQ), precision, accuracy, recoveries and stability were determined. LLOQs were 10 ng mL(-1) for M1, M2, M3, M4, and M5, respectively. Correlation coefficient (r) values for the linear range of 10-10,000 ng mL(-1) were greater than 0.999 for all the analytes. The intra-day and inter-day precision and accuracy were higher than 7.13%. The relative and absolute recovery was above 72% and no matrix effects were observed for all the analytes. This validated method provides a modern, rapid, and robust procedure for the pharmacokinetic studies of the pro-drugs after intravenous administration to rats. Some important results of AZT diaryl phosphate triester pro-drugs concerning chemical effect on pharmacokinetic performance are also studied.

The present investigation was aimed at lymphatic targeting of zidovudine (ZDV)-loaded surface-engineered liposomes (SE liposomes). Surface of liposomes was engineered by incorporation of charges (positive or negative) and site-specific ligand (mannose) in order to enhance localization to lymphatics, specifically to lymph node and spleen. Positively and negatively charged nanosized SE liposomes (120 +/- 10 nm) were prepared using stearylamine (SA) and dicetyl phosphate (DCP), respectively, while ligand-coated SE liposomes were prepared using mannose-terminated SA (mannose conjugate). The SE liposomes were characterized for shape and surface morphology, size, entrapment efficiency, and in vitro drug release. All the SE liposomes formulations showed biphasic ZDV release, whereas mannose-coated liposomes (MAN-Lip) significantly reduced (p < 0.05) drug release compared with conventional liposome (Lip). The organ distribution pattern of the SE liposomes exhibited significant reduction in free ZDV concentration in serum, whereas significantly increased quantity was detected in the spleen and lymph nodes (p < 0.05). Fluorescent microscopy suggested enhanced uptake and localization of the SE liposomes in the lymph nodes and spleen, which were in the order: mannose coated > negatively charged > positively charged > Lip. Thus, the SE liposomes appeared to be promising novel vesicular system for enhanced targeting of ZDV to lymphatics, in AIDS chemotherapy.

Many anti-human immunodeficiency virus 1 nucleoside reverse-transcriptase inhibitors have low central nervous system (CNS) distribution due in part to active efflux transport at the blood-brain barrier. We have previously shown that zidovudine (AZT) and abacavir (ABC) are in vitro substrates for the efflux transport protein breast cancer resistance protein (Bcrp) 1. We evaluated the influence of Bcrp1 on plasma pharmacokinetics and brain penetration of zidovudine and abacavir in wild-type and Bcrp1-deficient (Bcrp1-/-) FVB mice. There was no difference in either area under the concentration-time profiles for plasma (AUC(plasma)) or brain (AUC(brain)) for zidovudine between the wild-type and Bcrp1-/- mice. The AUC(plasma) of abacavir was 20% lower in the Bcrp1-/- mice, whereas the AUC(brain) was 20% greater. This difference resulted in a 1.5-fold increase in abacavir brain exposure in the Bcrp1-/- mice. The effect of selective and nonselective transport inhibitors on the ABC brain/plasma ratio at a single time point was evaluated. 3-(6-Isobutyl-9-methoxy-1,4-dioxo-1,2,3,4,6, 7,12,12a-octahydropyrazino[1',2':1,6]pyrido[3,4-b]indol-3-yl)-propionicacid tert-butyl ester (Ko143), N[4[2-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)ethyl]phenyl]-5-methoxy-9-oxo-10H-acridine-4-carboxamide (GF120918), probenecid, and Pluronic P85 increased abacavir plasma concentrations in the wild-type mice. Abacavir plasma concentrations in Bcrp1-/- mice were increased by (R)-4-((1aR,6R,10bS)-1,2-difluoro-1,1a,6,10b-tetrahydrodibenzo (a,e)cyclopropa(c)cycloheptan-6-yl)-alpha-((5-quinoloyloxy)methyl)-1-piperazineethanol trihydrochloride (LY335979), GF120918, and probenecid, but not by Ko143. Brain/plasma concentration ratios in both the wild-type and Bcrp1-/- mice were increased by the P-glycoprotein inhibitors LY335979 and GF120918, but not by BCRP-selective inhibitors. These data indicate that deletion of Bcrp1 has little influence on the pharmacokinetics or brain penetration of AZT. However, for abacavir, deletion of Bcrp1 reduces plasma exposure and enhances brain penetration. These findings suggest that Bcrp1 does not play a significant role in limiting the CNS distribution of zidovudine and abacavir; however, brain penetration of abacavir is dependent on P-glycoprotein-mediated efflux.

The remarkable sensitivity of accelerator mass spectrometry (AMS) is finding many new applications in pharmacology. In this study AMS was used to measure [(14)C]-Zidovudine (ZDV) concentrations at the drug's site of action (peripheral blood mononuclear cells, PBMCs) following a dose of 520 ng (less than one-millionth of the standard daily dose) to a healthy volunteer. In addition, the pharmacokinetics of this microdose were determined and compared to previously published parameters for therapeutic doses. Microdose ZDV pharmacokinetic parameters fell within reported 95% confidence intervals or standard deviations of most previously published values for therapeutic doses. Blood, urine, stool, saliva, and isolated PBMCs were collected periodically through 96 h postdose and analyzed for ZDV and metabolite concentrations. The results showed that ZDV is rapidly absorbed and eliminated, has one major metabolite, and is sequestered in PBMCs. (14)C mass balance assessments indicated a significant portion of ZDV remained after 96 h with a much prolonged elimination half-life. Results of this study demonstrate the usefulness of microdosing and AMS as a tool for studying the pharmacokinetic characteristics, including PBMC concentrations, of ZDV and underscore the value of AMS as a tool with which to perform pharmacokinetic and mass balance studies using trace amounts of radiolabeled compound.

Newborns from human immunodeficiency virus-infected mothers are given antiretroviral prophylaxis against mother-to-child transmission, including predominantly nucleoside reverse transcriptase inhibitors. Pharmacological monitoring of these drugs in newborns has so far been limited to plasma and cord blood. In this study, samples from newborns (up to 45 days old) treated with zidovudine (AZT) alone (n = 29) or in combination with lamivudine (3TC) (n = 20) were analyzed for both intracellular concentrations of phosphate metabolites in peripheral blood mononuclear cells and levels of parent drugs in plasma. Plasma AZT and intracellular AZT-monophosphate and AZT-triphosphate (TP) concentrations were significantly higher during the first 15 days of life (199 versus 52.7 ng/ml [P < 0.0001], 732 versus 282 fmol/10(6) cells [P < 0.0001], and 170 versus 65.1 fmol/10(6) cells [P < 0.0001], respectively) and then became comparable to those of adults. No difference in intracellular AZT metabolite concentrations was found when AZT- and AZT-3TC-treated groups were compared. Plasma 3TC levels (lower limit of quantification [LLOQ], 1,157 ng/ml; median, 412.5 ng/ml) were not associated with the newborn's age, gender, or weight. Intracellular 3TC-TP concentrations (LLOQ, 40.4 pmol/10(6) cells; median, 18.9 pmol/10(6) cells) determined for newborns receiving the AZT-3TC combination were associated with neither the age nor weight of the newborns. Concentrations in females were significantly higher (1.8-fold [P = 0.0415]) than those in males. Unexpectedly, newborns on AZT monotherapy whose mothers' treatment included 3TC displayed residual plasma 3TC and intracellular 3TC-TP levels up to 1 week after birth.

Human immunodeficiency virus (HIV)-infected patients often take herbal medicines, which may interact with antiretrovirals. American ginseng induces phase 2 and antioxidant enzymes in vitro and might increase the clearance of zidovudine and/or enhance antioxidant activity. Ten healthy volunteers received 300 mg of zidovudine orally before and after 2 weeks of treatment with a ginsenoside-enriched American ginseng extract 200 mg twice daily. This ginseng extract induced the phase 2 enzyme quinone reductase with an average concentration of doubling of enzyme activity of 190 microg/mL. Total ginsenoside content was 8.5 +/- 0.5%. Pharmacokinetic profiles of zidovudine and oxidative stress marker concentrations were measured post-zidovudine dose. American ginseng does not significantly affect the formation clearance of zidovudine to its glucuronide (ratio post- to pre-American ginseng = 1.17; 90% confidence interval: 0.95-1.45; P = .21), total clearance (ratio = 0.97; 0.82-1.14; P = .70), or plasma zidovudine AUC0-8 (ratio = 1.03; 0.87-1.21; P = .77). Oxidative stress biomarkers are reduced post-American ginseng (F2-isoprostane ratio = 0.79; 0.72-0.86; P < .001; 8-hydroxy-deoxyguanosine ratio = 0.74; 0.59-0.92; P = .02). Two weeks of American ginseng does not alter zidovudine pharmacokinetics but reduces oxidative stress markers.

Aims: To assess the effect of maraviroc on the pharmacokinetics of midazolam, a sensitive probe CYP3A4 substrate; lamivudine/zidovudine, a combination of nucleoside reverse transcriptase inhibitors (NRTIs); and ethinyloestradiol/levonorgestrel, a combination oral contraceptive., Methods: Three randomized, double-blind, placebo-controlled studies were conducted in healthy subjects to assess the effect of maraviroc on pharmacokinetics of other drugs. Two, two-period crossover studies were conducted to assess (i) the effect of steady-state maraviroc (300 mg b.i.d.) on pharmacokinetics of midazolam; and (ii) the effect of steady-state maraviroc (300 mg b.i.d.) on the pharmacokinetics of lamivudine/zidovudine. A third two-way crossover study was conducted to evaluate the effect of steady-state maraviroc (100 mg b.i.d.) on the pharmacokinetics of 30 microg ethinyloestradiol/150 microg levonorgestrel (Microgynon)., Results: The geometric mean ratios for C(max) and AUC for each of the compounds tested in the presence and absence of maraviroc were between 92% and 121%. There were no notable differences in T(max), t(1/2) or CL(R) (where measured) for any of the compounds., Conclusions: Maraviroc had no clinically relevant effects on the pharmacokinetics of the CYP3A4 substrate midazolam, the NRTIs zidovudine/lamivudine, or the oral contraceptive steroids ethinyloestradiol and levonorgestrel.

The aim of this study was to investigate a newly synthesized dextrin-zidovudine (AZT) conjugate designed as a sustained release prodrug of AZT for parenteral administration. AZT was first reacted with succinic anhydride to form a succinoylated AZT which was subsequently coupled with dextrin to yield the dextrin-AZT conjugate. The structure of the conjugate was characterized by FT-IR and (1)H-NMR spectroscopy. The drug content of the conjugate was 18.9 wt.%. The release in vitro of free AZT and succinoylated AZT was investigated in buffer solutions at pH 5.5 and 7.4 and in human plasma. AZT and succinoylated AZT release from the conjugate was 1.4% (pH 5.5), 41.7% (pH 7.4) and 78.4% in human plasma after 24 h. Release was complete in human plasma after 48 h. A pharmacokinetic study in rats following intravenous administration of the conjugate showed prolonged plasma levels of AZT compared to free AZT. The use of the conjugate extended the plasma half-life of AZT from 1.3 to 19.3 h and the mean residence time from 0.4 to 23.6 h. Furthermore, the conjugate provided a significant greater area under the plasma concentration-time curve and reduced the systemic clearance of AZT. This study suggested the potential of this novel dextrin-AZT conjugate as a new intravenous preparation of AZT.