Bioavailability of sulpiride tablet and capsule in dogs

The in vitro dissolution rates from four tablet formulations and one capsule formulation were measured in simulated gastric and simulated intestinal fluids. The dissolution t50% in simulated gastric fluid ranged from 1.5 min to 30 min and in simulated intestinal fluid, the values ranged from 4 to 228 min. The relative rates and rank order between products with regard to their dissolution rate were maintained. No correlation was obtained between in vitro dissolution rate and overall bioavailability in dogs as measured by the amounts of unchanged sulpiride excreted in the urine. The total unchanged sulpiride excreted in the 48 hr urine ranged from 30 to 44 % of the dose. The urinary half-lives ranged from 3.9 to 4.9 hr. The results indicate that, in the case of sulpiride, in vitro dissolution rate may not be a good predictor of bioavailability.