Intravenous injection of rocuronium produces intense discomfort at the site of injection in conscious patient. The purpose of this study was 2 folds; First, to determine the incidence of pain associated IV injection of rocuronium in adult patients. Second, to determine whether pretreatment with IV ondansetron affects the incidence of pain associated with the injection of rocuronium.

Eighty adult patients were randomly assigned to four groups. Before general anesthesia was induced with thiopental sodium (5 mg/ml), manual occlusion (70 mmHg) with tourniquet of venous inflow was performed. Randomly associated 20 patients received 4 ml of normal saline as a placebo control (Group 1). Other 60 patients allocated randomly to one of three groups: ondansetron 4 mg (Group 2), 6 mg (Group 3), 8 mg (Group 4) respectively. The patients' pain response to rocuronium injection was graded with using Memis' 4-point scale and withdrawal response was graded with using Kim's 4-point scale.

Nineteen patients (95%) in the group 1, 18 patients (90%) in the group 2, 19 patients (95%) in the group 3, and 14 patients (85%) in the group 4 reported pain. Moderate to sever pain was 17 patients (85%), in the group 1, 11 patients (55%) in the group 2, 9 patients (45%) in the group 3, and 1 patient (5%) in the group 4.

Ondansetron 4 mg, 6 mg, and 8 mg IV given before administration of rocuronium did not reduce incidence of pain on injection of rocuronium but significantly reduced severity of pain on injection of rocuronium and the 8 mg was more effective.