Pharmacokinetics and safety of clofazimine in children with rifampicin-resistant tuberculosis

Background Paediatric pharmacokinetic and safety data for clofazimine are limited. We described the pharmacokinetics and safety of clofazimine in South African children treated for multidrug/rifampicin-resistant tuberculosis (MDR/RR-TB). Methods Children <18 years being routinely treated for MDR/RR-TB were eligible for study participation. Soft gel capsules (Novartis Pharma AG) were administered using WHO-recommended weight-based dosing. Sparse and semi-intensive pharmacokinetic sampling was completed at baseline, Week 2 and 16. Clofazimine weekly area-under-the-concentration-time-curve (wAUC) was compared to target wAUC (60.87 mg*h/L and 111.79 mg*h/L) in adults receiving clofazimine 100mg daily for MDR/RR-TB and leprosy, respectively. Safety monitoring included measurement of QT-interval prolongation and laboratory assessment. Results Twenty children, six (30%) male, median age 6.0 years (range, 1.6-14.4), were included. Median clofazimine wAUC was 162.94 (IQR 130.06–263.95), >25% higher than the target adult wAUC in adults with MDR/RR-TB (111.79; IQR 81.9–151.9). No serious or grade ≥3 cardiac events occurred. There was a linear relationship between clofazimine concentration and QT-interval prolongation with an increase of 0.02 ms for every µg/L. There were 59 adverse events at least possibly related to clofazimine; one severe adverse event (elevated ALT) led to temporary withdrawal of clofazimine. Conclusions Clofazimine doses used achieved substantially higher exposures in children than adults receiving standard clofazimine doses. The association of higher clofazimine exposures and QT-interval prolongation may pose unnecessary risk to children, particularly in combination with other QT-prolonging drugs. Lower clofazimine doses to achieve appropriate clofazimine exposures should be investigated in children using different drug formulations and harmonised weight bands.