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 from 2 to less than 16 years and adult patients with FMF from 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 less than 4 years], 0.9 mg/day [from 4 to less than 6 years], 0.9 mg/day [from 6 to less than 12 years], 1.2 mg/day [from 12 to less than 16 years], and 1.2 mg/day [from 16 to less than 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 less than 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 less than 4, 6 to less than 12, and 12 to less than 16 years were similar to those in adults. However, mean AUC0?24h values in children 4 to less than 6 years were 25 percent 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 less than 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 less than 4 years was comparable to that in older children and adults.