Search

Background Moxifloxacin is a recommended drug for rifampin-resistant tuberculosis (RR-TB) treatment, but there is limited pediatric pharmacokinetic and safety data, especially in young children. We characterize moxifloxacin population pharmacokinetics and QT interval prolongation and evaluate optimal dosing in children with RR-TB. Methods Pharmacokinetic data were pooled from 2 observational studies in South African children with RR-TB routinely treated with oral moxifloxacin once daily. The population pharmacokinetics and Fridericia-corrected QT (QTcF)-interval prolongation were characterized in NONMEM. Pharmacokinetic simulations were performed to predict expected exposure and optimal weight-banded dosing. Results Eighty-five children contributed pharmacokinetic data (median [range] age of 4.6 [0.8–15] years); 16 (19%) were aged Conclusions Moxifloxacin doses above 10–15 mg/kg are likely required in young children to match adult exposures but require further safety assessment, especially when coadministered with other QT-prolonging agents.

Pharmacological interactions limit treatment options for children living with human immunodeficiency virus (HIV) and tuberculosis (TB). We found that 12 mg/kg twice daily raltegravir chewable tablets (administered after crushing) safely achieved pharmacokinetic targets in children living with HIV aged 4 weeks to Clinical Trials Registration NCT01751568.

Background In 2010, the World Health Organization (WHO) revised dosing guidelines for treatment of childhood tuberculosis. Our aim was to investigate first-line antituberculosis drug exposures under these guidelines, explore dose optimization using the current dispersible fixed-dose combination (FDC) tablet of rifampicin/isoniazid/pyrazinamide; 75/50/150 mg, and suggest a new FDC with revised weight bands. Methods Children with drug-susceptible tuberculosis in Malawi and South Africa underwent pharmacokinetic sampling while receiving first-line tuberculosis drugs as single formulations according the 2010 WHO recommended doses. Nonlinear mixed-effects modeling and simulation was used to design the optimal FDC and weight-band dosing strategy for achieving the pharmacokinetic targets based on literature-derived adult AUC0-24h for rifampicin (38.7–72.9), isoniazid (11.6–26.3), and pyrazinamide (233–429 mg ∙ h/L). Results In total, 180 children (42% female; 13.9% living with human immunodeficiency virus [HIV]; median [range] age 1.9 [0.22–12] years; weight 10.7 [3.20–28.8] kg) were administered 1, 2, 3, or 4 FDC tablets (rifampicin/isoniazid/pyrazinamide 75/50/150 mg) daily for 4–8, 8–12, 12–16, and 16–25 kg weight bands, respectively. Rifampicin exposure (for weight and age) was up to 50% lower than in adults. Increasing the tablet number resulted in adequate rifampicin but relatively high isoniazid and pyrazinamide exposures. Administering 1, 2, 3, or 4 optimized FDC tablets (rifampicin/isoniazid/pyrazinamide 120/35/130 mg) to children Conclusions Current pediatric FDC doses resulted in low rifampicin exposures. Optimal dosing of all drugs cannot be achieved with the current FDCs. We propose a new FDC formulation and revised weight bands.

BACKGROUND: High-dose isoniazid (INHH) (15–20 mg/kg/day) could be administered to overcome low-level INH resistance, but pharmacokinetic data are sparse.METHODS: This observational study included South African children (H as preventive therapy, or treatment for multidrug-resistant TB (MDR-TB) exposure or disease. Pharmacokinetic sampling was performed after an INH dose of 20 mg/kg. Non-compartmental analysis and multivariable regression models were used to evaluate associations of key covariates with area under the curve (AUC0–24) and maximum concentration (Cmax). AUC and Cmax values were compared against proposed adult targets.RESULTS: Seventy-seven children were included, with median age of 3.7 years; 51 (66%) had MDR-TB disease and 26 (34%) had MDR-TB exposure. Five were HIV-positive, of whom four were ≥5 years old. The median AUC0–24 was 19.46 µgh/mL (IQR 10.76–50.06) and Cmax was 5.14 µg/mL (IQR 2.69–13.2). In multivariable analysis of children aged 0–24 (geometric mean ratio GMR 0.19, 95% CI 0.15–0.26; P < 0.001) and Cmax (GMR 0.20, 95% CI 0.15–0.26; P < 0.001).CONCLUSIONS: INH concentrations in children with MDR-TB disease were much lower than expected, but comparable to previous reports in children with MDR-TB exposure. Further studies should confirm these findings and explore possible causes.

BackgroundRifampicin doses of 40 mg/kg in adults are safe and well tolerated, may shorten anti-TB treatment and improve outcomes, but have not been evaluated in children.ObjectivesTo characterize the pharmacokinetics and safety of high rifampicin doses in children with drug-susceptible TB.Patients and methodsThe Opti-Rif trial enrolled dosing cohorts of 20 children aged 0–12 years, with incremental dose escalation with each subsequent cohort, until achievement of target exposures or safety concerns. Cohort 1 opened with a rifampicin dose of 15 mg/kg for 14 days, with a single higher dose (35 mg/kg) on day 15. Pharmacokinetic data from days 14 and 15 were analysed using population modelling and safety data reviewed. Incrementally increased rifampicin doses for the next cohort (days 1–14 and day 15) were simulated from the updated model, up to the dose expected to achieve the target exposure [235 mg/L·h, the geometric mean area under the concentration–time curve from 0 to 24 h (AUC0–24) among adults receiving a 35 mg/kg dose].ResultsSixty-two children were enrolled in three cohorts. The median age overall was 2.1 years (range = 0.4–11.7). Evaluated doses were ∼35 mg/kg (days 1–14) and ∼50 mg/kg (day 15) for cohort 2 and ∼60 mg/kg (days 1–14) and ∼75 mg/kg (day 15) for cohort 3. Approximately half of participants had an adverse event related to study rifampicin; none was grade 3 or higher. A 65–70 mg/kg rifampicin dose was needed in children to reach the target exposure.ConclusionsHigh rifampicin doses in children achieved target exposures and the doses evaluated were safe over 2 weeks.

Safety concerns persist for long-term pediatric fluoroquinolone use. Seventy children (median age, 2.1 years) treated with levofloxacin 10–20 mg/kg once daily for multidrug-resistant tuberculosis (median observation time, 11.8 months) had few musculoskeletal events, no levofloxacin-attributed serious adverse events, and no Fridericia-corrected QT interval >450 ms. Long-term levofloxacin was safe and well tolerated.

Background Linezolid is increasingly important for multidrug-resistant tuberculosis (MDR-TB) treatment. However, among children with MDR-TB, there are no linezolid pharmacokinetic data, and its adverse effects have not yet been prospectively described. We characterised the pharmacokinetics, safety, and optimal dose of linezolid in children treated for MDR-TB. Methods and findings Children routinely treated for MDR-TB in 2 observational studies (2011–2015, 2016–2018) conducted at a single site in Cape Town, South Africa, underwent intensive pharmacokinetic sampling after either a single dose or multiple doses of linezolid (at steady state). Linezolid pharmacokinetic parameters, and their relationships with covariates of interest, were described using nonlinear mixed-effects modelling. Children receiving long-term linezolid as a component of their routine treatment had regular clinical and laboratory monitoring. Adverse events were assessed for severity and attribution to linezolid. The final population pharmacokinetic model was used to derive optimal weight-banded doses resulting in exposures in children approximating those in adults receiving once-daily linezolid 600 mg. Forty-eight children were included (mean age 5.9 years; range 0.6 to 15.3); 31 received a single dose of linezolid, and 17 received multiple doses. The final pharmacokinetic model consisted of a one-compartment model characterised by clearance (CL) and volume (V) parameters that included allometric scaling to account for weight; no other evaluated covariates contributed to the model. Linezolid exposures in this population were higher compared to exposures in adults who had received a 600 mg once-daily dose. Consequently simulated, weight-banded once-daily optimal doses for children were lower than those currently used for most weight bands. Ten of 17 children who were followed long term had a linezolid-related adverse event, including 5 with a grade 3 or 4 event, all anaemia. Adverse events resulted in linezolid dose reductions in 4, temporary interruptions in 5, and permanent discontinuation in 4 children. Limitations of the study include the lack of very young children (none below 6 months of age), the limited number who were HIV infected, and the modest number of children contributing to long-term safety data. Conclusions Linezolid-related adverse effects were frequent and occasionally severe. Careful linezolid safety monitoring is required. Compared to doses currently used in children in many settings for MDR-TB treatment, lower doses may approximate current adult target exposures, might result in fewer adverse events, and should therefore be evaluated., Using data from two cohorts, Anthony Garcia-Prats and colleagues model the appropriate dosing necessary to achieve target concentrations for linezolid to treat children with multidrug-resistant tuberculosis., Author summary Why was this study done? Linezolid is an antibiotic that has recently been repurposed for the treatment of multidrug-resistant tuberculosis (MDR-TB). Based on emerging data from clinical trials, it is now recommended for inclusion as a priority in treatment regimens for adults and children. There is a lack of evidence-based dosing guidelines for linezolid in children for MDR-TB. Linezolid has frequent adverse effects that are associated with higher doses and longer durations of treatment, but this has not been well described in children treated for MDR-TB. What did the researchers do and find? We assessed linezolid pharmacokinetics (concentrations) and safety among children routinely treated for MDR-TB from 2 observational studies. We modelled this pharmacokinetic data and simulated the doses in children that would be needed to achieve current targets. Doses supported by our data for some weight bands were lower than currently in use, which may reduce the risk of adverse effects. Linezolid-related adverse effects were frequent—with low haemoglobin being the most common—and occasionally severe (grade 3 or 4). What do these findings mean? Revised linezolid doses supported by this study now provide an evidence base for international dosing recommendations. All linezolid-treated children with MDR-TB should have careful safety monitoring to include at least regular haemoglobin monitoring. Larger studies, evaluating the revised dosing, are needed to better characterise linezolid safety and to assess the risk of more rare linezolid-related events, especially given the small number of children in this study.

ObjectivesTo evaluate the proportion of children with lopinavir Cmin ≥1 mg/L when receiving a novel 8-hourly lopinavir/ritonavir dosing strategy during rifampicin co-treatment.MethodsHIV-infected children on lopinavir/ritonavir and rifampicin were enrolled in a prospective pharmacokinetic study. Children were switched from standard-of-care lopinavir/ritonavir-4:1 with additional ritonavir (1:1 ratio) twice daily to 8-hourly lopinavir/ritonavir-4:1 using weight-banded dosing. Rifampicin was dosed at 10–20 mg/kg/day. After 2 weeks, plasma samples were collected ∼2, 4, 6, 8 and 10 h after the morning lopinavir/ritonavir-4:1 dose, ALT was obtained to assess safety and treatment was switched back to standard of care. ClinicalTrials.gov registration number: NCT01637558.ResultsWe recruited 11 children in two weight bands: 5 (45%) were 10–13.9 kg and received 20–24 mg/kg/dose of lopinavir and 6 (55%) children weighed 6–9.9 kg and received 20–23 mg/kg/dose of lopinavir. The median age was 15 months (IQR = 12.6–28.8 months). The median (IQR) lopinavir Cmin was 3.0 (0.1–5.5) mg/L. Seven (63.6%) of the 11 children had Cmin values ≥1 mg/L. Children with a lopinavir mg/kg dose below the median 21.5 were more likely to have Cmin ConclusionsThese data do not support the use of 8-hourly lopinavir/ritonavir at studied doses. Evaluation of higher doses is needed to optimize treatment outcomes of TB and HIV in young children.

Levofloxacin is increasingly used in the treatment of multidrug-resistant tuberculosis (MDR-TB). There are limited pediatric pharmacokinetic data to inform dose selection for children. Children routinely receiving levofloxacin (250-mg adult tablets) for MDR-TB prophylaxis or disease in Cape Town, South Africa, underwent pharmacokinetic sampling following receipt of a dose of 15 or 20 mg/kg of body weight given as a whole or crushed tablet(s) orally or via a nasogastric tube. Pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling. Model-based simulations were performed to estimate the doses across weight bands that would achieve adult exposures with 750-mg once-daily dosing. One hundred nine children were included. The median age was 2.1 years (range, 0.3 to 8.7 years), and the median weight was 12 kg (range, 6 to 22 kg). Levofloxacin followed 2-compartment kinetics with first-order elimination and absorption with a lag time. After inclusion of allometric scaling, the model characterized the age-driven maturation of clearance (CL), with the effect reaching 50% of that at maturity at about 2 months after birth and 100% of that at maturity by 2 years of age. CL in a typical child (weight, 12 kg; age, 2 years) was 4.7 liters/h. HIV infection reduced CL by 16%. By use of the adult 250-mg formulation, levofloxacin exposures were substantially lower than those reported in adults receiving a similar dose on a milligram-per-kilogram basis. To achieve adult-equivalent exposures at a 750-mg daily dose, higher levofloxacin pediatric doses of from 18 mg/kg/day for younger children with weights of 3 to 4 kg (due to immature clearance) to 40 mg/kg/day for older children may be required. The doses of levofloxacin currently recommended for the treatment of MDR-TB in children result in exposures considerably lower than those in adults. The effects of different formulations and formulation manipulation require further investigation. We recommend age- and weight-banded doses of 250-mg tablets of the adult formulation most likely to achieve target concentrations for prospective evaluation.