Pharmacokinetics of tiaprofenic acid in children after a single oral dose

Twelve healthy children in three age groups anaesthetized for minor surgery were given a single oral dose of tiaprofenic acid (3 mg.kg-1) (TA). Seven blood samples and zero to 8 and 8 to 24 h urines were collected. TA concentrations in plasma and urine were measured by HPLC. No significant difference was found between the age groups in the kinetic parameters of TA and no correlation was found between these parameters and age: tmax = 2.12 h, Cmax = 8.78 mg.l-1, AUC(0----8 h) 33.9 mg.h.l-1, AUC = 39.3 mg.h.l-1, t1/2 = 2.35 h, Vt = 0.319 l.kg-1, CL = 0.094 l.h-1.kg-1. Renal clearance was 14 ml.h-1.kg-1.33% of the TA dose was recovered in the 24 h urine, 48% of which was conjugated, whereas in adults, TA is only found in urine as conjugates. The apparent plasma clearance was significantly higher (56%) than in 12 healthy adults given 1.5 mg.kg-1 TA. Volume of distribution and t1/2 did not significantly differ between children and adults. Since no relationship has been established between plasma TA and either efficacy or toxicity, a different dose regimen cannot be recommended in 3-11 year-old children from that in adults.