Effect of an aluminium-hydroxide containing antacid on the oral bioavailability of pirenzepine

Abstract

The effect of an antacid containing aluminium-hydroxide, magnesium-hydroxide and calcium carbonate (Trigastril®) on the bioavailability of orally administered pirenzepine (Gastricur®) was evaluated in 10 subjects in a double-blind single dose cross-over study. Pirenzepine was assayed in plasma by a highly sensitive high-performance liquid chromatographic method. A 2-compartment model was taken as a basis for the calculation of the plasma concentration curves and the pharmacokinetic parameters. The oral bioavailability of a 50 mg pirenzepine tablet concomitantly administered with 10 ml of the antacid gel preparation was slightly but not significantly greater than that of pirenzepine in the presence of a placebo gel. This was reflected by a mean increase of 18-28% in area under the curve (AUC 0-32, AUC 0-∞, resp.) and of 26% in C(max) values. There was no significant difference in the biological half-life of pirenzepine between the two treatments (10.1-9.4 h).