Abstract
The in vitro interactions of procainamide, verapamil, guanethidine and hydralazine with some commercial adsorbent antacids and anti-diarrhoeal preparations were studied. Kaopectate was found to adsorb procainamide, verapamil, guanethidine and hydralazine with a limiting adsorptive capacity of 16.67, 15.15, 9.62 and 20.12 mg/g, respectively, while magnesium trisilicate was found to adsorb the same drugs with a limiting adsorptive capacity of 20.08, 25.13, 33.9 and 100 mg/g respectively. The limiting adsorptive capacity of hydralazine and guanethidine on Pepto-Bismol were 84.03 and 12.5 mg/g while Simeco adsorbed hydralazine with a limited capacity of 26.2 mg/g. Peak salivary procainamide concentration in humans were decreased by about 31% and the AUC was decreased by about (32%) on concurrent administration of kaopectate with the drug. These interactions could lead to important differences in bioavailability of the above drugs.