Background and Aims: We compared the block characteristics between dexmedetomidine versus buprenorphine as an adjuvant to bupivacaine in ultrasound guided supraclavicular brachial plexus block. Duration of sensory and motor block along with duration of analgesia were the primary endpoints. Materials and Methods: A comparative two group randomized clinical study was designed in which sixty ASA 1 and ASA 2 patients who were scheduled for elective upper limb surgeries under ultrasound guided supraclavicular brachial plexus block were randomly divided into two equal groups. Group D (n=30), received 24 ml 0.5% bupivacaine + 1 ml (50 μg) dexmedetomidine and Group B (n=30), received 24 ml 0.5% bupivacaine + 1 ml (100 μg) buprenorphine. Duration of sensory, motor blockade and analgesia were assessed along with onset of sensory and motor blockade, sedation, and side effects among the two groups. Results: Duration of sensory and motor block in Group D (588.7±38.2 & 481.7±16.8) was longer than Group B
(395.7±15.5 & 334.3±23.8; p <0.001). Duration of analgesia in Group D (805.7±54.1) was longer than Group B (579.0±41.4). There was no significant difference among the groups with respect to onset of sensory and motor blockade. Bradycardia was observed in one patient in Group D and vomiting was seen in two patients in Group B, no other adverse effects were observed. Conclusion: Dexmedetomidine prolongs the duration of sensory and motor blockade and duration of analgesia as compared with buprenorphine when used as an adjuvant to bupivacaine in supraclavicular brachial plexus block, with no adverse side effects.