Patients were more likely to report a complete absence of nausea and vomiting with cannabis than with placebo, and there was little discernable difference between the effectiveness of cannabinoids and of prochlorperazine, metoclopramide, domperidone, and chlorpromazine. Notably, however, none of the trials involved the agents now most widely used—the serotonin 5-HT3 antagonists. The National Comprehensive Cancer Network guidelines cautiously mention cannabinoids as a
breakthrough treatment for chemotherapy-induced nausea and vomiting not responsive to other antiemetics.