Effects of different hepatic pathologies on disposition of alfentanil in anaesthetized patients

We have studied the influence of different hepatic pathologies on the disposition of alfentanil in 23 unpremedicated patients (six healthy control subjects, six patients with liver dysfunction of alcoholic aetiology and 11 patients with non-alcohol related liver disease). All patients received a bolus of alfentanil 500 micrograms i.v. as supplement to 67% nitrous oxide and isoflurane in oxygen anaesthesia. Plasma drug concentrations were measured in venous blood samples at intervals up to 24 h by radio-immunoassay and protein binding was determined by equilibrium dialysis. Kinetic estimates were determined using non-compartmental analysis. Patients with non-alcoholic liver disease had lesser plasma clearance (114.8 (range 66.8-213.5) ml min-1) than the alcoholic group (158.8 (100.0-220.7) ml min-1) or controls (187.4 (125.2-269.5) ml min-1). In all three groups, there was considerable intersubject variability, with a bimodal distribution in the non-alcoholic group. This group also had a smaller apparent volume of distribution at steady state. Mean residence time was prolonged in the alcoholic group compared with controls (284.9 (217.8-362.2) min vs 226.8 (201.2-250) min). Protein binding was decreased in the alcoholic group compared with controls (84.9 (SD 4.2)% vs 89.3 (2.1)%); this was attributable to a lesser plasma alpha 1-acid glycoprotein concentration (0.55 (0.18) g litre-1 vs 0.89 (0.21) g litre-1). Free drug clearance was reduced in both liver dysfunction groups compared with controls.