BackgroundStudies have suggested that 5-hydroxytryptamine-3A (5-HT-3A) receptor antagonists may have analgesic effects. This randomized, double-blind, placebo-controlled, factorial study tested the hypothesis that 5-HT-3A receptor antagonist tropisetron attenuates post-operative pain in women receiving either sevoflurane or propofol based anaesthesia. MethodsTwo hundred and ninety-six women undergoing gynaecological laparoscopies were randomly assigned to be anaesthetized with either sevoflurane or propofol. Immediately after the induction of anaesthesia, the anaesthesiologist administered either tropisetron 2mg or a placebo intravenously. Pain score at rest at 0.5h post-operatively reported using a numerical rating scale was the primary outcome measure. The secondary outcome measures included pain score at rest every 2h within the first 24h post-operatively, duration of post-anaesthesia care unit stay, incidence of post-operative nausea and vomiting, the incidence of shivering and score of the Quality of Recovery Score 40. ResultsCompared with placebo, tropisetron produced a statistically significant decrease on pain report within the first 6h post-operatively in the sevoflurane-based anaesthesia group (3 [2, 4] vs. 5 [4, 5], p<0.001 in 0.5h; 2 [0, 4] vs. 3 [3, 5], p<0.001 in 2h; 2 [0, 3] vs. 3 [1, 4], p=0.002 in 4h; 1 [0, 3] vs. 2 [1, 4], p=0.016 in 6h), but not in the propofol-based group. ConclusionsA single-dose intravenous administration of tropisetron after anaesthesia induction is associated with statistically significant decreased early post-operative pain in patients undergoing gynaecological laparoscopies under sevoflurane based general anaesthesia.