Effect of food and antacids on the oral absorption of pirenzepine in man

Abstract

The effect of food or an aluminum and magnesium hydroxide antacid on the bioavailability of orally administered pirenzepine was evaluated in 20 subjects in a 4-way crossover study. The extent of oral bioavailability of a 50 mg pirenzepine tablet administered following a 10 h fast was significantly (ANOVA, P < 0.05) greater than that of pirenzepine in the presence of either food or antacids. This was reflected by a mean reduction of 30% in area under the curve (AUC 0 → 48h) when pirenzepine was administered either one-half hour before a meal, with a meal or with a liquid antacid preparation. It was also observed that pirenzepine peak plasma concentrations were reduced by 30% with concomitant food, or by 45% when concomitant antacids were administered. The rate of absorption, measured as the reduction in time to reach peak plasma concentration, was significantly (ANOVA, P < 0.05) greater when pirenzepine was given either with a meal or one-half hour before a meal, than when administered following a 10 h fast or with antacid. There was no significant difference in the biological half-life of pirenzepine among the four treatments (range 12.1 – 12.9 h).