Pharmacokinetics of rioprostil in rats.

The pharmacokinetics of rioprostil in rats has been investigated following a single intravenous or oral dose of rioprostil between 0.004 and 10 mg/kg. Rioprostil is eliminated from plasma following an intravenous dose rapidly (t1/2 = 0.22 h) and nearly exclusively by biotransformation. The high total clearance (CL = 5.4 l.h-1.kg-1) indicates an additional extrahepatic metabolism. A systemic bioavailability of 2%, in spite of a rapid and nearly complete absorption (fa = 90%), indicates an extended first-pass effect. Twenty-four hours after the administration of [3H]rioprostil the residual radioactivity in the animal amounted to less than 1% of the dose administered.