The selective &bgr;1-adrenoceptor antagonist metoprolol is eliminated primarily by hepatic metabolism and usually less than 5% of an oral dose is excreted unchanged in the urine.The effects of impaired liver function on the pharmacokinetics of metoprolol were studied in 10 patients with hepatic cirrhosis. All subjects were given single doses of 20mg intravenously and 50mg orally on separate days. The mean fraction of the drug available systematically was 84 ± 10% in patients and 50 ± 11% in a control group of 6 healthy subjects (p < 0.05). The total body clearance of metoprolol in the cirrhotics was 0.61 ± 0.13L/min and in the controls 0.80 ± 0.11L/min. These values correspond to elimination half-lives of 7.2 ± 1.2 and 4.2 ± 1.1 hours, respectively. The differences were not statistically significant. Impaired liver function had no effect on the volume of distribution of metoprolol. Total body clearance was weakly but linearly related to galactose clearance (r2= 0.52; p < 0.05), and the half-life was related to serum bilirubin (r2= 0.74; p < 0.01).