In vitro antidiabetics-antacid interactions.

The adsorption of the oral antidiabetics metformin hydrochloride, glibenclamide, acetohexamide, tolbutamide, carbutamide, tolazamide and glymidine on various antacids or adsorbents was studied at 37 degrees C. The antacids or adsorbents used were magnesium trisilicate, aluminium hydroxide, calcium carbonate, magnesium oxide, bismuth oxycarbonate, talc, kaolin as well as charcoal. None of the substances tested, with the exception of charcoal, exhibited superior adsorptive properties for all the drugs. Magnesium trisilicate and calcium carbonate were the best adsorbents for metformin hydrochloride. Acetohexamide and glibenclamide were adsorbed to an appreciable extent on most antacids. Tolbutamide showed an adsorption tendency towards talc. Most antacids slightly adsorbed carbutamide, while magnesium trisilicate showed a higher adsorption capacity for tolazamide and glymidine. The dissolution rate of acetohexamide in magnesium oxide suspension (5:400) increased about 40-fold after 10 min, whle in magnesium trisilicate suspension (5:400) it increased about 7-fold. On the other hand, magnesium trisilicate did not influence the dissolution rate of metformin hydrochloride. The probable variation in the bioavailability of orally administered antidiabetics when coadministered with antacids was discussed. However, further in vivo studies are needed before a final assessment for such drug-antacid interaction can be confirmed.