Pharmacokinetics and clinical experience of 20-h infusions of methohexitone in intensive care patients with postoperative pyrexia. We have studied the pharmacokinetics of 20-h infusions of methohexitone in young patients with postoperative fever undergoing artificial ventilation of the lungs. The infusion rate was adjusted so that patients were unresponsive to vocal stimulation but reacted to tracheal suction. The mean steady state concentration of methohexitone required was 2.6 mg litre-1 (unbound 0.53 mg litre-1). The mean (SD) total clearance of methohexitone was 16.3 (4.2) ml min-1 kg-1, which is greater than that for volunteers or normal surgical patients. The unbound clearance correlated positively with body temperature during the infusion (r = 0.796, P = 0.017). The terminal half-life of methohexitone was 6.3 (3.8) h and that of the 4'-hydroxy metabolite 5.8 (2.1) h. There were no marked haemodynamic effects of the infusion, and no excessive sedation after the infusion. However, the clearance of methohexitone was high and variable, possibly as a direct effect of postoperative fever. Consequently, the need for individual titration of the rate of infusion is emphasized. 