Abstract
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 Cmax 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 AUC0-24h values in children 2 to <4, 6 to <12, and 12 to <16 years were similar to those in adults. However, mean AUC0-24h 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.