comparing intravenous lidocaine, ondansetron and their combination on reducing pain of injection of propofol

background: propofol is a widely used intravenous anesthetic drug. one of its side effects is pain during injection. we investigate the effects of intravenous ondansetron, lidocaine, and their combination on pain reduction of intravenous propofol. methods: eighty eight women with asa class (american society of anesthesiologists) classification i-ii patients undergoing elective gynecologic surgeries allocated into four equal groups including normal saline, lidocaine, ondansetron, and the combination of two drugs. all drugs were prepared in the same volume of 5 ml. pain during propofol injection after intravenous injection of study drugs was assessed using numeric rating scale (nrs). demographic data and pain scores were recorded and compared in all patients. results: the overall incidence of pain on propofol injection was lower in lidocaine (4%), ondansetron (9%) and combination group (zero) than in saline group (72%) (p=0.001). sixteen patients (72%) in saline group had moderate to severe pain. two patients (9%) in ondansetron group and one patient (4%) in lidocaine group had mild pain (p= 0.06). no patient in lidocaine, ondansetron and combination group had moderate to severe pain (p>0.05). conclusion: pretreatment with ondansetron with or without lidocaine is effective in preventing pain from propofol injection.