RESUMO
In the present study, a floating and sustained release formula composed of 1:1 of verapamil to HPMC, 5% of gas generating mixture [anhydrous citric acid and sodium hydrogen carbonate] and prepared by wet granulation with 96% alcohol followed by compression was chosen from a previous study for in-vivo evaluation in comparison with a commercial controlled release product of verapamil hydrochloride. Investigations have been undertaken in beagle dogs to evaluate both the intra-gastric retention performances using x-ray and the bioavailability of the drug from both test and standard tablets. Results showed that the floating formula was able to delay the gastric emptying of verapamil tablet in beagle dogs for more than 4 hours compared to almost 1 hour for a control tablet devoid of the gel forming polymer and the gas generating mixture. The floating tablets showed bioequivalence with a commercial sustained release tablet [Manidon[R] 120 retard] with higher mean AUC[0]-omega and Cmax and longer tmax, however, non-significantly different. It was concluded that the delayed gastric emptying observed with the floating tablets would maximize absorption by allowing the slowly released drug in the stomach to reach the sight of absorption at the upper small intestine in a form ready for absorption