Ondansetron 8 mg and 4 mg with normal saline against post-operative headache and nausea/vomiting after spinal anesthesia: a randomized double-blind trial.

The study aims to evaluate the efficacy of ondansetron in preventing post-spinal headache, considering the high prevalence of the headache in pregnant women and the common use of the adjuvants for prophylaxis against post-operative nausea and vomiting (PONV). This double-blind clinical trial included the 195 patients who were referred to Taleghani Hospital (in Arak, Iran) for cesarean section (C/S) under spinal anesthesia, and then the subjects were assigned to three equally sized groups using block randomization. Participants in the first, second, and control groups received 8 mg, 4 mg of ondansetron, and normal saline, respectively, 5 minutes before surgery. A final volume of 5 cc was prepared by adding normal saline. Participants were examined for headache one week after surgery, and then data analysis was performed using SPSS 20. The incidence of post-spinal headache was significantly higher in the placebo group than in the ondansetron 8-mg and 4-mg groups at 24 hours after surgery (P < 0.010). But, no significant difference was observed between two ondansetron groups (P ≤ 0.05). The overall incidence of the headache was generally lower in ondansetron 8-mg (26.66% vs. 33.68.05%) and 31.66% in ondansetron 4-mg (P < 0.001). Moreover, the PONV incidence was significantly higher in the placebo group than in the other two groups at 24 hours (P < 0.001). The hemodynamic variables were same in three groups. The ondansetron 8-mg dose can be effective to prevent headache after spinal anesthesia for C/S. Moreover, the ondansetron 8-mg and ondansetron 4-mg have same effect in control of PONV after spinal anesthesia for C/S.