The pharmacokinetics of sustained release tiaprofenic acid in elderly arthritic patients.

Tiaprofenic acid is a non-steroidal anti-inflammatory drug which is highly protein bound and excreted mainly by the kidneys. Previous pharmacokinetic studies with tiaprofenic acid in conventional formulations in elderly arthritic patients have shown no evidence of accumulation of this drug over periods of up to 12 weeks. A sustained release formulation of the drug was given to 14 elderly arthritic patients over 4 weeks and plasma profiles obtained at the beginning and end of treatment over a 24 h period. Area under the curve (AUC), maximum plasma concentration (Cmax) and plasma concentration at 24 h (C24) were calculated and elimination half life (t1/2) was estimated. AUCs to infinity at week 0 were compared with AUCs to infinity at week 4 as a measure of drug accumulation. No significant differences were found for any of these parameters between the beginning and end of treatment. The mean t1/2 for both weeks was approximately 4.4 h. There was no evidence of any accumulation.