Background: Intrathecal   adjuvant drugs are utilized with local anesthetics to  relieve post-operative pain.
Aim of the study: Current study compared intra-and post-operative effects of Intrathecal nalbuphine versus fentanyl as adjuvants to bupivacaine during lower body surgeries in elderly.
Patients and Methods: Seventy subjects scheduled for elective lower body surgeries were randomly allocated to receive 2.5 ml of hyperbaric bupivacaine with either 0.8mg nalbuphine [group N], 20µg fentanyl [group F] intrathecally. Intra- and post-operative data collected and compared between groups.  The first analgesic request as the primary outcome.  Hemodynamic changes, total post-operative analgesic consumption, pain, sensory and motor blocks and associated adverse events were recorded as secondary outcome.      
Results: Onset of sensory block was significantly delayed in N group [7.1±1.2 min] compared  to F group [5.7±1.2 min]  . Time to achieve maximum block height in group N was 12.7±2.2 min compared 10.3±1.8 min in group F  .  Mean time to two segment regression was significantly prolonged in N group [239.7±41.4 min] than F group [223.4±17.6] with [p=0.035]. The onset and duration of motor block were significantly faster in group F [7.6±1.15 min and 201 ± 17 min] compared to group N [8.7±0.86 min and 215 ± 26 min]  .First analgesic request was significantly delayed in N group [267±25 min.] compared to F group [246±18 min.] . Total amount of ketorolac and Pethidine consumption in 24 h postoperatively was significantly lesser in N group compared to F group.
Conclusion: Nalbuphine intrathecally at a dose of 0.8 mg is as effective as fentanyl at a dose 20 µg when used as an intrathecal adjuvant to bupivacaine for lower body surgeries. The prolonged duration of analgesia and no adverse effects makes it a good choice in lower limb surgeries in elderly.