Steady state pharmacokinetics of piroxicam in children with rheumatic diseases.

Ten children with rheumatoid arthritis, aged 7-16 y and weighing 20-63 kg, were treated with piroxicam mean dose 0.4 mg.kg-1 once daily for 2 weeks. On Day 15, blood was sampled from 2-120 h after the last dose. The Cmax for piroxicam ranged from 3.6 to 9.8 (mean 6.6) mg.l-1 and its half-life by log linear computation was 22 to 40 (mean 32.6) h. The volumes of distribution and the total body clearance were estimated as the ratio of actual volumes of distribution and actual clearances to availability. The volumes of distribution (V/F) were 0.12 to 0.25 (mean 0.16) l.kg-1, and the total body clearances (CL/F) were 2.1 to 5.0 (mean 3.4) ml.kg-1.h-1. Thus, piroxicam clearance in these patients was higher and its half-life was shorter than those previously reported in young adults, yet V appeared similar.