Pharmacokinetics of colchicine in pediatric and adult patients with familial mediterranean fever

This study sought to determine the appropriate starting dose of colchicine in children aged 2 to 4 years with familial Mediterranean fever (FMF) based on steady-state pharmacokinetics in pediatric patients with FMF ≥2 to <16 years and adult patients with FMF ≥16 to ≤65 years. Outpatients received colchicine for 90 days starting with a fixed dose for 14 days (blood sampling days 14 and 15). After starting doses of colchicine (0.6 mg/day [≥2 to <4 years], 0.9 mg/day [≥4 to <6 years], 0.9 mg/day [≥6 to <12 years], 1.2 mg/day [≥12 to <16 years], and 1.2 mg/day [≥16 to ≤65 years]), the observed steady-state pharmacokinetic parameters were comparable across age groups, despite the higher doses of colchicine on a mg/kg/day basis in the younger age groups. An exception occurred with once-daily colchicine, whereby mean C_max for colchicine was higher in patients 4 to <6 years (9.4 ng/mL) compared with the younger and older age groups (6.1-6.7 ng/mL). Mean AUC_0-24h values in children 2 to <4, 6 to <12, and 12 to <16 years were similar to those in adults. However, mean AUC_0-24h values in children 4 to <6 years were 25% higher than those observed in adults. The results show that the recommended starting dose for children 2-4 years and 4-6 years should be 0.6 mg/day (half the US adult dose). Children aged 6 to <12 years should receive 0.9 mg/day (i.e. three-quarters of the US adult dose). The safety of colchicine in children 2 to <4 years was comparable to that in older children and adults.