Bioavailability of 14C-sulpiride in dogs

The plasma and urinary concentrations of unchanged 14C-sulpiride were measured in the dog following i.v. and oral administration. Bioavailability of the oral hydrochloride solution was 85% and that of the free base suspension was 75%. Sulpiride equilibrated rapidly with tissue fluid and had an apparent volume of distribution of 3.3--3.8 1/kg. The plasma half-life was 2.5--3 hours. The short plasma half-life and its negligible concentrations in the brain are consistent with the low lipophilicity of supliride. When 100 mg sulpiride was given orally either as hydrochloride or free base, the maximum plasma level was reached within one hour and concentrations were 2.3 and 1.8 micrograms/ml, respectively. The similarity of urinary excretion data from i.v. and oral preparations suggest minimal "first-pass" effect.