Cannabinoids in the treatment of chemotherapy-induced nausea and vomiting: beyond prevention of acute emesis.

Chemotherapy-induced nausea and vomiting (CINV) remains a significant problem in the care of cancer patients. Although the use of serotonin (5-HT3) receptor antagonists, as well as neurokinin-1 inhibitors, has reduced rates of acute emesis, many patients still experience acute vomiting; moreover, these agents have reduced efficacy in preventing nausea, delayed CINV, and breakthrough CINV. Nausea, in particular, continues to have a major--and often overlooked--impact on patients' quality of life. Optimizing the treatment for CINV likely will involve combinations of agents that inhibit the numerous neurotransmitter systems involved in nausea and vomiting reflexes. Cannabinoids are active in many of these systems, and two oral formulations, dronabinol (Marinol) and nabilone (Cesamet), are approved by the US Food and Drug Administration for use in CINV refractory to conventional antiemetic therapy. Agents in this class have shown superiority to dopamine receptor antagonists in preventing CINV, and there is some evidence that the combination of a dopamine antagonist and cannabinoid is superior to either alone and is particularly effective in preventing nausea. The presence of side effects from the cannabinoids may have slowed their adoption into clinical practice, but in a number of comparative clinical trials, patients have expressed a clear preference for the cannabinoid, choosing its efficacy over any undesired effects. Improvement in antiemetic therapy across the entire spectrum of CINV will involve the use of agents with different mechanisms of action in concurrent or sequential combinations, and the best such combinations should be identified. In this effort, the utility of the cannabinoids should not be overlooked.