Abstract: Background and purpose: The main and the most known complication of intravenous regional anesthesia (IVRA) is systemic toxicity due to local anesthetics that occurs following the accidental tourniquet release immediately after injection. This study aims to evaluate the effect of adding ketamine to lower dose of lidocaine on reducing the dose and side effects of lidocaine. Materials and Methods: In this randomized clinical trial, 60 patients undergoing the surgery of upper limb below the elbow under IVRA were randomly divided into two groups. In group 1 (control group), 40 ml lidocaine 0.5% (200 mg) and in group 2 (intervention group), 40 ml lidocaine 0.25% (100 mg) plus 40 mg of ketamine 0.1% injected intravenously. Outcomes included postoperative pain at 15, 30 and 60 minutes after surgery. The pain of the patients was assessed by using the Visual Analogue Scale (VAS Score). Results: Both groups were comparable in demographic and surgical parameters. The average pain based on the VAS score at 15, 30 and 60 minutes after surgery was similar in both groups and there was no significant difference between the two groups (p> 0.05). Moreover, postoperative complications including unconsciousness, restlessness, dizziness, nausea, vomiting, tinnitus, seizure, delirium and hallucination had no significant differences (p> 0.05). Conclusion: Results of this study showed that the addition of ketamine to lower dose of lidocaine in patients receiving IVRA significantly reduced postoperative pain, and reduces the likelihood of systemic toxicity with lidocaine without causing significant adverse effects.Abstract: Background and purpose: The main and the most known complication of intravenous regional anesthesia (IVRA) is systemic toxicity due to local anesthetics that occurs following the accidental tourniquet release immediately after injection. This study aims to evaluate the effect of adding ketamine to lower dose of lidocaine on reducing the dose and si...Show More