Optimal single sampling time-point for monitoring of praziquantel exposure in children

Praziquantel pharmacokinetics studies in schistosomiasis infected children are scarce partly due to the challenges/complexity of intensive blood sampling in the target population. This study was aimed to investigate the optimal single sampling time-point for monitoring praziquantel exposure. This was intensive pharmacokinetic study conducted among 32 Schistosoma mansoni infected children treated with an oral standard single-dose 40 mg/kg praziquantel. Plasma samples were collected at 0, 1, 2, 4, 6 and 8 h post-praziquantel administration. Quantification of praziquantel and its enantiomers ( R- and S- praziquantel) concentrations was done by Liquid chromatography-tandem mass spectrometer (LC–MS/MS). The correlation between area under the plasma concentration–time curve from 0 to 8 h (AUC 8 ) and plasma concentrations at each specific sampling time-point was determined by Pearson’s correlation coefficient (r 2 ). The median age (range) of the study population was 12.5 years (10–17). The study participants were 17 males and 15 females. Both total praziquantel and its enantiomers ( R- and S- praziquantel) displayed a wide inter-individual pharmacokinetic variability. Regression analysis indicated that, plasma concentrations collected at 4 h post-dose had a significantly highest correlation with the AUC 8 for both total praziquantel (r 2 = 0.81, p < 0.001) and S- praziquantel (r 2 = 0.84, p < 0.001) than any other sampling time-point; while for R- praziquantel, plasma concentrations collected at 6 h sampling time-point had a significantly highest correlation with the AUC 8 (r 2 = 0.79, p < 0.001) than any other sampling time-point. Four hours sampling time-point post-praziquantel administration is ideal optimal single sampling time-point for therapeutic monitoring of total praziquantel exposure while 6 h sampling time-point is suitable for monitoring of a pharmacologically active R- praziquantel enantiomer.