Indirect assessment of the enterohepatic recirculation of piroxicam and tenoxicam.

To assess the extent of enterohepatic recycling of piroxicam and tenoxicam, their pharmacokinetics have been compared in the absence and presence of concomitant treatment with cholestyramine. In a randomized crossover study 6 healthy volunteers received piroxicam and tenoxicam 20 mg p.o., alone or with cholestyramine 24 g/day for 4 days. Cholestyramine increased piroxicam & tenoxicam elimination approximately 2-fold (t 1/2 50.3 vs 28.1 h and 73.6 vs 35.8 h, respectively). It also increased the apparent clearance (Cl/f) of piroxicam and tenoxicam by 58% and 112%. When cholestyramine was administered, the t 1/2 of piroxicam & tenoxicam were correlated (r = 0.89), which suggests that their hepatic biotransformation is under a common control. It is concluded that: piroxicam and tenoxicam are eliminated to a large and comparable extent through the biliary route, and the administration of cholestyramine may help to accelerate their elimination in cases of overdosage.