Pharmacokinetics of sulpiride after oral and intravenous administration in the rat and the dog.

The plasma concentration of sulpiride was measured in the rat and in the dog after oral and i.v. administration of the drug. In the rat only traces (less than 1 mug/ml) of sulpiride were detected in plasma after an oral dose of 100 mg/kg. The peak concentrations in 3 dogs given 25, 50 or 100 mg/kg orally were 6.1, 15.6 and 23.9 mug/ml, respectively. The pharmacokinetic data after i.v. injection were compared to earlier observations with the related orthopramide compound, metoclopramide. The half-life of sulpiride in dog plasma (1.6 -- 3.4 hr) is longer than that of metoclopramide, but in the rat there is little difference between the two compounds. Both of the compounds have large total apparent volumes of distribution (1-2 1/kg) in the two species. The marked species difference in the systemic bioavailability of oral sulpiride should be taken into account when the orthopramide drugs are evaluated in pharmacological tests.