Cotter, J. (2009). Efficacy of crude marijuana and synthetic delta-9-tetrahydrocannabinol as treatment for chemotherapy-induced nausea and vomiting: A systematic literature review. Oncology Nursing Forum, 36, 345–352.

To determine if oral synthetic tetrahydrocannabinol (THC) and smoked marijuana are effective in the treatment of chemotherapy-induced nausea and vomiting (CINV), and to evaluate the side effects and patient preferences for treatment

Databases searched were MEDLINE (1966–present), CINAHL (1982–present), and the Cochrane Library.  A search of article reference lists also was performed.

Search keywords were nausea, vomiting, cancer, chemotherapy, cannabis, marijuana, and dronabinol.

Studies were included in the review if they

• Reported on human clinical trials.
• Involved treatment with smoked marijuana or oral synthetic THC for CINV.
• Were in English.

The author retrieved 18 relevant citations, 10 of which were clinical trials and included in the review. The author evaluated the quality of the reference based on strength of evidence, study design, sample size, and purpose. Specific criteria were not described.

• A total of 929 patients were involved across the 10 included studies.
• Sample sizes ranged from 15 to 214.
• Subjects had a variety of diagnoses and were receiving various types of chemotherapy.
• Six studies involved the use of chemotherapy that was of moderate to high emetogenic potential.

• Two studies evaluated the efficacy of oral synthetic THC versus placebo. In both studies, THC was significantly better than placebo at reducing CINV (p < 0.001).
• A one-group study tested crude marijuana; 78% of patients reported it to be moderately or highly effective. However, 18 patients dropped out of the study because they did not accept the smoking route of administration.
• Three studies examined oral synthetic THC versus phenothiazines. Two of these studies found that THC was significantly more effective in controlling CINV (p < 0.05) while the third found no difference. Timing and dosages differed across studies. In one study, patients who took THC reported significantly more sedation, incoordination, and feelings of being high than those receiving compazine or placebo.
• One study found that the combination of THC and antiemetics was most successful in mitigating severity and duration of CINV.
• In one study of smoked marijuana versus phenothiazines, no differences were found between groups.
• In a comparison of oral THC versus smoked marijuana, both were found to be effective with no significant differences found between these approaches.
• One study compared oral THC versus 5-HT₃ receptor antagonists (RAs) in a randomized, controlled, double-blind design. All patients received a standard antiemetic protocol of dexamethasone and ondansetron prior to chemotherapy and then were randomly assigned to also receive THC, placebo, or other drugs alone or in combination. All drugs were more effective than placebo, but no significant differences were found between those who took the THC and the other medication groups.
• A number of these studies had small sample sizes, and one lacked a control group.

• Both oral THC and smoked marijuana were found to be more effective than placebo and as equally effective as other commonly used antiemetics in controlling CINV.
• Oral THC appears to be as effective as smoked marijuana.
• THC was associated with more side effects (sedation, lack of coordination, and feeling “high”).
• Some patients found the inhalation route for marijuana use to be unacceptable.
• Some patients may not be able to tolerate the harsh smoke, and, because crude marijuana may contain bacteria or fungi, concerns exist for immunocompromised patients.
• Cannabinoids appear to have value as adjuvant medication, and the evidence supports their use for mitigation of CINV. They appear to be most effective in combination with other antiemetics.

Nurses need to review potential sides effects. Individual patients can have differing concerns as a result of other problems or preferences. Oral THC may be the best option for use among patients with cancer.