BackgroundThe primary purpose of this investigation was to determine the relative potency of eltanolone, a new steroid hypnotic, and propofol and thiopental when used for induction of general anesthesia. In addition, the induction characteristics of propofol and eltanolone were compared.MethodsOne hundred seventy-five patients, premedicated with lorazepam 1 mg orally, randomly received one of six different doses of either eltanolone or propofol. The probability of successful induction (deined as not responsive to verbal commands within 2 min) was related to the logarithm of the dose for each drug by means of logistic regression analysis. Estimates of ED50and ED95for each drug were obtained. The incidence of side effects was compared for eltanolone and propofol. The potency of thiopental was determined in a parallel study, using an identical methodology in 105 patients receiving one of seven different doses of the barbiturate.ResultsThe relative potency of eltanolone was 3.2 times (95% confidence interval 2.7–3.8) greater than propofol and 6.0 times (5.3–6.9) greater than thiopental. ED50and ED95values for eltanolone were 0.46 (0.40–0.52) and 0.82 (0.68–1.28) mg.kg–1, respectively. Compared to propofol, induction of anesthesia with eltanolone is characterized by a lower incidence of injection pain (3.5%vs.58%) and apnea (1.2%vs.11.2%).ConclusionsEltanolone appeared to be an effective induction agent that is 3.2 times more potent than propofol and 6 times more potent than thiopental. Its use was associated with less pain on injection than was propofol.