BACKGROUND: The aim of this randomized, double-blind, placebo-controlled study was to evaluate dose effects of ephedrine pretreatment on the onset time and intubating conditions after cisatracurium administration. METHODS: A total of 140 adult patients were randomized into 4 groups to receive either 30 microg/kg ephedrine (Group 30, n = 35), 70 microg/kg ephedrine (Group 70, n = 35), 110 microg/kg ephedrine (Group 110, n = 35), 3 ml normal saline (Group C, n = 35) as pretreatment given 30 s before anesthetic induction. Neuromuscular block was achieved with 0.15 mg/kg cisatracurium, evaluated accelomyographically with train-of-four stimulation. An anesthesiologist blinded to patient grouping assessed the intubating conditions 1.5 min after cisatracurium administration. RESULTS: An onset time of 70 s was obtained in the ephedrine groups (Group 30: 155.4 +/- 44.7 s, Group 70: 152.6 +/- 40.3 s, Group 110: 151.2 +/- 51.6 s) compared to Group C (224.6 +/- 56.9 s) after 0.15 mg/kg of cisatracurium (P < 0.001). Ephedrine doses of either 70 or 110 microg/kg for pretreatment significantly improved intubating conditions (P < 0.05). Systolic and diastolic blood pressure and heart rate at 1 min after tracheal intubation were significantly increased than other times in all groups (P < 0.001), with no differences among the groups. However, 5 patients in Group 110 experienced marked hypertension (systolic/diastolic blood pressure: > 200/100 mmHg) 1 min after tracheal intubation with no patients in other groups. CONCLUSIONS: We conclude that pre-treatment with ephedrine 70 microg/kg improved intubating conditions 1.5 min after cisatracurium administration and facilitated the onset of neuromuscular block (70 s) without adverse hemodynamic effects.