Objective: Rocuronium is a steroidal muscle relaxant with an intermediate duration and rapid onset of action. Pain on injection of rocuronium is common, occurring in 70%–90% of patients. In this study, we compared the efficacy of metoclopramide and ketamine alone and as combinations with lidocaine in preventing pain caused by the injection of rocuronium.

Materials and Methods: Sixty patients aged between 18 to 65 years and American Society of Anaesthesia (ASA) physical status I or II were randomly divided into four groups (n=60). Group I received ketamine 5 mg+lidocaine 20 mg, Group II metoclopramide 10 mg+lidocaine 20 mg, Group III metoclopramide 10 mg, and Group IV ketamine 5 mg respectively. All solutions were diluted to 5ml with normal saline. Venous occlusion was applied for 30 seconds using a forearm tourniquet then solutions was injected over a period of 10 seconds, and 15 s after the administration of the study drug, the tourniquet was released. Then, 10 mg rocuronium was injected iv over 10 s, and patients were asked if they had pain, and extremity movement was assessed.

Results: The overall incidence of rocuronium-induced pain on injection was significantly less in Group I than the other Groups (p<0.001). 15 patients (100%) in the Group I, 10 (66.7%) in the group II, 3 (20%) in the Group III, and 4 (26.7%) in the Group IV reported no pain. Frequency of withdrawal response after rocuronium was 0 % in the Group I and II, 20% in the Group III and IV, respectively.

Conclusion: We concluded that lidocaine–ketamine combination is most effective for preventing the pain on rocuronium injection.