Objective: To determine the efficacy of prophylactic administration of intravenous Ondansetron for prevention of spinal anaesthesia induced hypotension in lower segment caesarean section.

Material and Methods: One hundred patients were selected for this study, and randomly divided in two groups of 50 each, using random numbers table. Both groups were preloaded with Ringer’s lactate at dose of 10ml/kg. Group A received 04 mg of IV ondansetron 5 min prior to spinal anaesthesia, whereas Group B received normal saline 05 minutes before administration of Spinal Anaesthesia.

Results: Average age of Group A was 28.62 ± 4.64 years, whereas that of Group B was 27.88 ± 3.98 (p–value= 0.394). Average weight of Group A was 70.30 ± 6.25 kg, whereas that of Group B was 70.74 ± 6.17 kg (p–value= 0.724). Hypotension was noted in 21 patients in group A (42%), whereas it was observed in 34 Patients in Group B (68%) (p–value= 0.009). Bradycardia was noted in 9 patients in Group A (18%) and 19 patients in Group B (p=0.026).

Conclusion: Intravenous administration of 04 mg of intravenous ondansetron, 05 minutes prior to subarachnoid block, is effective in decreasing frequency of hypotension.