OBJECTIVES: Ropivacaine local injection is a preventative management option for post-adenotonsillectomy pain. The effectiveness of this approach varies depending on the time of drug administration. This study is aimed to evaluate pre-emptive effect of administration of Ropivacaine before vs. after adenotonsillectomy. METHODS: In this study, children aged 3-12 years who were diagnosed with chronic tonsillitis candidates for elective adenotonsillectomy surgery randomly assigned to one of three randomized groups. Participants in the first group got a peritonsillar injection of 3 mg/kg Ropivacaine 1 % before the surgery, patients in the second group received 3 mg/kg Ropivacaine 1 % peritonsillar injection after surgery, and patients in the control group received peritonsillar injections of 5 cc normal saline. Postoperative pain was assessed using the Wong-Baker Pain Scale. SPSS software was used to perform statistical analysis. RESULTS: Among total of 99 enrolled cases, mean age of 7.29 ± 2.61 years, participants who received Ropivacaine before surgery experienced significantly less postoperative pain four, eight, and 24 h after surgery (P = 0.002). In addition, compared to other groups, these patients consumed significantly less analgesics during postoperative hospitalization and after discharge (p <
0.002 and = 0.002 respectively). CONCLUSION: Ropivacaine peritonsillar injection before adenotonsillectomy may be more beneficial than Ropivacaine injection after surgery for postoperative pain management among children undergoing adenotonsillectomy.