Efficacy of isoniazid in paediatric tuberculosis: an individual participant data meta-analysis.

BACKGROUND: Isoniazid is a cornerstone of management therapy for tuberculosis (TB). Our aim was to determine the association between isoniazid exposure and clinical outcomes, to develop a pharmacokinetic model, and to optimise the dosing regimen in children treated for drug-susceptible (DS)-TB.

METHODS: For this individual participant data meta-analysis, PubMed was searched for observational studies, involving children (aged 0-18 years), being treated for DS-TB. The relationship between isoniazid exposure and clinical outcomes was analysed using a mixed effects logistic regression model. Pharmacokinetic parameters were described using non-linear mixed effects modelling. The pharmacokinetic target was the median adult area under the concentration-time curve at steady-state (AUC) of 23.4 mg·h·L.

RESULTS: Six studies provided clinical outcomes, including 405 patients, of which 21% had unfavourable outcomes. 16 studies (1255 patients) were included in the pharmacokinetic model. Unfavourable outcomes were only related to lower body mass index (BMI) for age z-score (BAZ) (OR 0.96, 95% CI 0.93-0.99; p<0.05). Isoniazid exposure was impacted by-acetyltransferase 2 (NAT2) genotype, weight, age and nutritional status (using BAZ). With currently recommended World Health Organization (WHO) doses, isoniazid exposure was similar to that of adults. Pharmacokinetic target attainment was 71.7% and 29.5% for slow and fast metabolisers, respectively (p<0.05); 50.5% for patients with BAZ >0 and 42.6% for malnourished patients (BAZ <&#x2009;-2) (p<0.05). The model-informed dosing regimen showed that fast metabolisers could benefit from higher isoniazid dosing, especially in malnourished children.

CONCLUSION: Our findings showed that the only predictor of unfavourable clinical outcomes was a lower BAZ. We support the current WHO-recommended dosing regimen for isoniazid. To equalise and attain our pharmacological target for all children, dosing regimens could be adjusted on NAT2 genotype and nutritional status.