Ondansetron for the prevention of seasickness in susceptible sailors: An evaluation at sea

Background: Seasickness is a common problem, causing a significant decrement in performance among naval crew. In about 20-60% of crewmembers, symptoms appear with varying intensity depending on the sea state and the duration of the voyage. Recent studies have suggested antiemetic 5HT₃ blockers as a possible treatment for motion sickness, emphasizing their minor clinical and cognitive side effects. The purpose of the present study was to evaluate the 5HT1 blocker ondansetron in the prevention of seasickness. Methods: There were 16 volunteers with a normal otoneurologic examination and no previous medical history of inner ear disease or vertigo who took part in a double blind, randomized, crossover study. During an initial learning phase, the participants practiced on a battery of computerized performance tests until their results stabilized. Ondansetron 8 mg or placebo was administered 2 h before sailing aboard a 500-ton naval vessel in mild sea conditions. Participants did the performance tests and completed a questionnaire evaluating their seasickness symptoms 4 h into the voyage. Results: No statistically significant reduction of seasickness symptoms was demonstrated between ondansetron treatment and placebo (a Wiker score of 2.69 ± 1.78 and 2.81 ± 1.97, respectively). There was no statistically significant difference in side effects or the results of the performance tests. Conclusion: In this study, ondansetron was not found to be beneficial in the treatment of seasickness. It could be speculated that the mechanism of nausea in seasickness is different from that of toxin-induced nausea.