Improved intestinal absorption of sulpiride in rats with synchronized oraldelivery systems

The goals of this study were to examine whether formulations. capable of re leasing sulpiride (SP) in synchrony with the p-Glycoprotein (P-gp) inhibito rs, verapamil (Ver) or quinidine (Qn) can increase SP relative bioavailabil ity and to suggest a rationals approach for oral administration of SP. Jeju num of anesthetized rats was perfused with 200 or 400 mug/ml of SP either a lone or together with 98 mug/ml of Ver. It was observed that while an incre asing SP concentration did not cause an increase in SP blood levels, the ad dition of Ver or Qn to the perfusion solution caused a profound increase in SP absorption. Erodible matrix tablets. exhibiting a range of erosion rate s, were prepared by manipulating the ratios of hydroxypropylmethylcellulose (HPMC) in the matrices. The tablets were designed to release the low water soluble SP and the highly water soluble Qn concomitantly over 1. 2 or 4 h. In all cases, the synchronous release increased SP bioavailability after i ntra-intestinal administration. The increase varied from 2.6- to 3.9-fold f or the fast and the slow release formulations, respectively (compared with a control administration of a powdered mixture of SP and Qn). It is specula ted that the poor oral bioavailability of SP was caused by brush border P-g p efflux. Synchronous release delivery systems of SP containing also the P- gp inhibitor Qn were able to increase SP bioavailability after intestinal a dministration in the rat. It is concluded that oral bioavailability of poor ly absorbed drugs, in which absorption is restricted by gut wall secretory transport, may be improved by formulating them with functional adjuvants in synchronous release drug carriers. (C) 2001 Elsevier Science B.V. All righ ts reserved.