Antiemetic efficacy of smoked marijuana: subjective and behavioral effects on nausea induced by syrup of ipecac.

Although the public debate about the legalization of marijuana has continued for as long as 25 years, few controlled studies have been conducted to assess its potential medical benefits. The present study examined the antiemetic effect of smoked marijuana cigarettes (8.4 and 16.9 mg Delta(9)-tetrahydrocannabinol [THC]) compared to a highly potent antiemetic drug, ondansetron (8 mg) in 13 healthy volunteers. Nausea and emesis were induced by syrup of ipecac. Marijuana significantly reduced ratings of "queasiness" and slightly reduced the incidence of vomiting compared to placebo. Ondansetron completely eliminated the emetic effects of ipecac. These findings support and extend previous results, indicating that smoked marijuana reduces feelings of nausea and also reduces emesis in this model. However, its effects are very modest relative to ondansetron, and the psychoactive effects of marijuana are likely to limit its clinical usefulness in the general population.