Absorption and excretion of suprofen in rats

DL-2-(4-(2-Thienylcarbonyl)phenyl)propionic acid (suprofen, S) was rapidly absorbed in rats after oral administration. Blood levels after a single oral dose of 2, 10, 50, or 100 mg/kg of 3H-S reached maxima within 30 min and were dose-dependent. The major portion of the drug was shown to be absorbed from the upper part of the small intestine and a portion from the stomach. The radioactivity in rat plasma was extensively bound to the plasma protein in vivo; this was found to be unchanged S and four metabolites. Elimination of S and its metabolites from blood was rapid; 3H was mostly excreted in the urine and feces within 24 hr after oral administration of 3H-S. No significant amounts of 14CO2 were excreted in expired air after administration of 14C-S. Rat urine contained S and four metabolites found in rat plasma, accounting for about 60% of the urinary radioactivity. After rats with biliary fistulas were given an oral dose of 2 mg/kg of 3H-S, 41% of the dose was excreted in the bile during 48 hr; there was significant enterohepatic circulation. When single or 21 consecutive daily doses of 3H-S were administered to rats, the blood levels after the multiple doses were higher than those after a single dose but no significant difference was found in excretion of 3H.