[Prevention of fentanyl rebound by administration of cimetidine (author's transl)]

Pre- and intraoperatively 8 orthopaedic patients were given cimetidine in order to raise the pH of gastric juice. Following an 0.5 mg i.v. bolus injection of fentanyl at the beginning of anaesthesia, the pH of the gastric juice and plasma concentrations of fentanyl were measured. After oral medication with cimetidine 400 mg on the evening prior to anaesthesia and an i.v. administration of 200 mg/h during the course of an enflurane-N2O-anaesthesia no secondary peak of plasma fentanyl concentration was observed. Thus it would seem possible to prevent fentanyl sequestration into the stomach and consecutively gastro-entero-systemic recirculation by administration of cimetidine. While duration and half-life of the alpha-phase are prolonged, the half-life of the beta-phase (150 min) remains almost unchanged. This pharmacokinetic effect is explained by an altered biodisposition.