Pragmatic global dosing recommendations for the 3-month, once-weekly rifapentine and isoniazid preventive TB regimen in children

Effectiveness and pharmacokinetic exposures of first-line drugs used to treat drug-susceptible tuberculosis in children: a systematic review and meta-analysis

BACKGROUND

Optimal doses of first line drugs for drug-susceptible tuberculosis (DS-TB) treatment in children and young adolescents remain uncertain. We aimed to determine if children treated using WHO-recommended or higher doses of first-line drugs achieve successful outcomes and sufficient pharmacokinetic exposures.

METHODS

Titles, abstracts, and full-text articles were screened. We searched Pubmed, EMBASE, CENTRAL, and trial registries from 2010 to 2021. We included studies in children <18 years, being treated for DS-TB with rifampicin, pyrazinamide, isoniazid, and ethambutol. Outcomes were treatment success rates and drug exposures. The protocol for the systematic review was preregistered in PROSPERO, CRD42021274222.

RESULTS

Of 304 studies identified, 46 studies were eligible for full-text review and 12 and 18 articles were included for the efficacy and pharmacokinetic analysis, respectively. Of 1,830 children included in the efficacy analysis, 82% had favourable outcomes (range 25%-95%). At WHO-recommended doses, exposures to rifampicin, pyrazinamide, and ethambutol were lower in children as compared to adults. Children ≤6 years have 35% lower AUC than older children (14.4 (9.9-18.8) vs 22.0 (13.8-30.1) μg.h/mL) and children with HIV (CWHIV) had 35% lower rifampicin AUC than HIV negative children (17.3 (11.4-23.2) vs 26.5 (21.3-31.7) μg.h/mL). Heterogeneity and small sample sizes were major limitations.

CONCLUSION

There is large variability in outcomes with an average 82% favourable outcomes. Drug exposures are lower in children than in adults. Younger children and CWHIV are underexposed to rifampicin. Standardization of pharmacokinetic paediatric studies and individual patient data analysis with safety assessment are needed to inform optimal dosing.

Pharmacometrics in tuberculosis: progress and opportunities

Tuberculosis remains one of the leading causes of death by a communicable agent, infecting up to one-quarter of the world's population, predominantly in disadvantaged communities. Pharmacometrics employs quantitative mathematical models to describe the relationships between pharmacokinetics and pharmacodynamics, and to predict drug doses, exposures, and responses. Pharmacometric approaches have provided a scientific basis for improved dosing of antituberculosis drugs and concomitantly administered antiretrovirals at the population level. The development of modelling frameworks including physiologically-based pharmacokinetics, quantitative systems pharmacology and machine learning provides an opportunity to extend the role of pharmacometrics to in silico quantification of drug-drug interactions, prediction of doses for special populations, dose optimization and individualization, and understanding the complex exposure-response relationships of multidrug regimens in terms of both efficacy and safety, informing regimen design for future study. In this short clinically-focused review, we explore what has been done, and what opportunities exist for pharmacometrics to impact tuberculosis pharmacotherapy.

Emerging data on rifampicin pharmacokinetics and approaches to optimal dosing in children with tuberculosis

INTRODUCTION

Despite its longstanding role in tuberculosis (TB) treatment, there continues to be emerging rifampicin research that has important implications for pediatric TB treatment and outstanding questions about its pharmacokinetics and optimal dose in children.

AREAS COVERED

This review aims to summarize and discuss emerging data on the use of rifampicin for: 1) routine treatment of drug-susceptible TB; 2) special subpopulations such as children with malnutrition, HIV, or TB meningitis; 3) treatment shortening. We also highlight the implications of these new data for child-friendly rifampicin formulations and identify future research priorities.

EXPERT OPINION

New data consistently show low rifampicin exposures across all pediatric populations with 10-20 mg/kg dosing. Although clinical outcomes in children are generally good, rifampicin dose optimization is needed, especially given a continued push to shorten treatment durations and for specific high-risk populations of children who have worse outcomes. A pooled analysis of existing data using applied pharmacometrics would answer many of the important questions remaining about rifampicin pharmacokinetics needed to optimize doses, especially in special populations. Targeted clinical studies in children with TB meningitis and treatment shortening with high-dose rifampicin are also priorities.