Population pharmacokinetics and dosing of dispersible moxifloxacin formulation in children with rifampicin‐resistant tuberculosis

Aims Moxifloxacin is a priority drug for treating rifampicin‐resistant tuberculosis (RR‐TB). We assessed the pharmacokinetics of a child‐friendly, dispersible 100 mg tablet moxifloxacin formulation (dispersed in water) compared to the standard 400 mg non‐dispersible formulation (crushed and suspended in water) in children and evaluated current dosing recommendations. Methods The CATALYST trial investigated the pharmacokinetics of moxifloxacin in children with RR‐TB. Children were enrolled in South Africa, India and the Philippines. Intensive pharmacokinetic sampling was undertaken while children were taking the standard non‐dispersible 400 mg moxifloxacin tablet formulation and repeated after switching to the novel dispersible formulation. Pharmacokinetic data were analysed using population pharmacokinetic modelling. Simulations were performed to evaluate moxifloxacin exposures in children compared to consensus adult reference exposures using current World Health Organization (WHO)‐recommended doses and more recent model‐based doses. Results Thirty‐six children were enrolled [median age 4.8 (range 0.4–15) years and weight 15.6 (range 6.9–42.1) kg]. A two‐compartment disposition model with first‐order elimination and delayed absorption was developed. The bioavailability of dispersible versus standard formulations fulfilled standard bioequivalence criterion (ratio 1.05 with 90% confidence interval 0.95–1.15). Simulations showed WHO‐recommended doses achieved exposures similar to those in adults in children >10 kg, while children <10 kg may require 33%–56% higher doses to reach adult reference exposures. Conclusions Dosing recommendations for children can be the same for the dispersible paediatric and standard non‐dispersible adult moxifloxacin formulation. The current WHO dosing recommendation risks underdosing moxifloxacin in children <10 kg. We propose optimized moxifloxacin doses for both formulations.