Improving the oral bioavailability of sulpiride by sodium oleate in rabbits

To improve the limited oral bioavailability of sulpiride, a dosage form containing sodium oleate as an absorption enhancer was developed and evaluated using gastric-emptying-controlled rabbits in a cross-over manner. In addition to the known properties of sodium oleate with respect to modifying the permeability of biomembranes, it was found to be capable of improving the physicochemical properties of sulpiride toward a higher lipophilicity (by ion-pair association) and a higher solubility (by micellar solubilization). Nonetheless, the incorporation of sodium oleate with sulpiride as a mixture filled in hard gelatin capsules failed to increase intestinal absorption, whereas the use of enteric capsules, instead of the hard gelatin capsules resulted in a significant increase (P < 0.05) in the oral bioavailability.