This prospective, double-blind, randomized, placebo-controlled study was designed to determine the efficacy of dexmedetomidine compared with lidocaine in reducing the pain of propofol and rocuronium injection pain.

One hundred and fifty patients, scheduled for elective surgery with general anaesthesia, were divided into five groups: saline (Group 1), dexmedetomidine 0.25 μg kg−1 (Group 2), lidocaine 0.5 mg kg−1 (Group 3), dexmedetomidine 0.25 μg kg−1 plus lidocaine 0.25 mg kg−1 (Group 4) or dexmedetomidine 0.25 μg kg−1 plus lidocaine 0.5 mg kg−1 (Group 5) were administered at a rate of 0.5 mL s−1 after tourniquet application. The occlusion was released after 1 min and 5 mL of propofol was injected over 20 s. Pain was evaluated by use of a 10-point verbal analogue scale. Then, the rest of the induction dose of propofol, 3 mL of saline bolus and 0.6 mg kg−1 of rocuronium, was injected. The response to injection of rocuronium was assessed with a four-point scale (0–3).

Groups 1 and 2 were found to have higher propofol injection pain scores than Groups 3, 4 and 5 (P < 0.05). When the study groups were compared according to the overall incidence of withdrawal movements due to rocuronium (⩾1 response) in Groups 1, 2, 3, 4 and 5, they were different (86.7%, 60%, 36.7%, 50% and 40%, respectively) (P < 0.05). Except Group 1, there was no significant difference between the groups according to incidence of withdrawal movement after rocuronium injection (P = 0.325).

Pretreatment with dexmedetomidine is not effective in reducing injection pain of propofol, but may attenuate the hand withdrawal associated to rocuronium, as lidocaine does.