Pirenzepin does not alter the pharmacokinetics of theophylline

The possible pharmacokinetic interactions between pirenzepin and theophylline were investigated in an open single blind trial. Aminophylline (6.5 mg/kg body weight) was administered intravenously in five healthy male volunteers before and after chronic oral pirenzepin therapy (50 mg twice daily 5 days before to 2 days after giving aminophylline). To study the theophylline pharmacokinetics, serum and urine samples were collected up to 48 hours after aminophylline administration. It was demonstrated, that pirenzepin does not affect theophylline pharmacokinetics. Therefore, pirenzepin may be combined with aminophylline or theophylline without the risk of an interaction, which usually affect the coadministration of other antiulcer drugs, e.g. cimetidine, with theophylline.