Complex Formation of Cimetidine with Caffeine in Aqueous Solutions

Abstract

The dissolution profiles of cimetidine, a cimetidine-caffeine complex, and a cimetidine-caffeine physical mixture were determined in 0.3% HC1 and distilled water at 37°. The cirnetidine-caffeine physical mixture had a dissolution rate similar to that of the cimetidine alone while the complex had a slower dissolution rate. Partioning experiments were conducted using either 0.3% HC1 or pH 6.7 buffer solution as the polar phase and chloroform as the non-polar phase. The apparent partition coefficient of cimetidine was decreased in the presence of caffeine added either as free caffeine or as a cimetidine-caffeine complex.