Efficacy and safety of intrathecal clonidine vs fentanyl added to bupivacaine for lower abdominal procedures

Intrathecal adjuvants such as fentanyl and clonidine may enhance the quality and duration of spinal anaesthesia and postoperative analgesia with bupivacaine, but their comparative efficacy and side-effect profiles remain important. The present study aimed to compare the effects of intrathecal fentanyl and clonidine as adjuvants to 0.5% bupivacaine on block characteristics, postoperative analgesia, haemodynamic, sedation, and adverse effects in patients undergoing lower abdominal surgery. This randomised double-blind comparative study was conducted in the Department of Anaesthesiology, Balrampur Hospital, Lucknow, among 96 patients aged 18-60 years, ASA physical status I-II, scheduled for lower abdominal surgeries. Patients were randomly allocated into three groups (n= 32 each): Group B received 2.5 mL of 0.5% bupivacaine with 0.5 mL normal saline, Group F received 2.5 mL of 0.5% bupivacaine with fentanyl 25 ug, and Group C received 2.5 mL of 0.5% bupivacaine with clonidine 30 ug. Outcomes included block onset and duration, rescue analgesia time, VAS score, haemodynamic, sedation, and adverse events. Baseline characteristics were comparable among groups. Group C showed the fastest onset of sensory block (1.45 ± 0.30 min) and the longest duration of sensory block (150.23 ± 28.47 min), followed by Group F and Group B (p< 0.0001). A similar pattern was observed for motor block onset and duration (p < 0.0001). Time to first rescue analgesia was significantly prolonged in Group C (6.00 ± 1.50 h) compared with Group F (4.50 ± 1.22 h) and Group B (2.80 ± 0.76 h) (p < 0.0001). Postoperative VAS scores were significantly lower in Group C. Haemodynamic variables remained largely comparable. Sedation was higher with clonidine, with marked sedation observed only in Group C. Intrathecal clonidine 30 ug with bupivacaine provided better block characteristics and longer postoperative analgesia than fentanyl 25 ug or bupivacaine alone, but with higher sedation Received: 25.12.2025 | Revised: 23.04.2026 | Accepted: 26.05.2026