Anorexia is a significant problem in more than half of advanced cancer patients, causing a lack of appetite and weight loss. Although anecdotal evidence suggests that smoking cannabis can stimulate appetite, its effects on appetite and weight gain in patients with cancer cachexia have not been studied. Two early studies found that oral THC (dronabinol) improved appetite and food intake in some patients undergoing cancer chemotherapy. An open-label study of dronabinol (2.5 mg Δ9-THC, two to three times daily, four to six weeks) in patients with unresectable or advanced cancer reported increases in appetite and food intake, but weight gain was limited to a few patients. Modest weight gain was achieved with a larger dosing regimen of dronabinol (5 mg t.i.d.), but CNS side effects such as dizziness and somnolence were significant limiting factors. In contrast, a randomized, double-blind, placebo-controlled study in cancer patients with anorexia-cachexia syndrome showed no difference in appetite across treatment categories (oral cannabis extract, Δ9-THC, or placebo). Moreover, compared to megestrol acetate, an orexigenic medication, dronabinol was significantly less effective in improving appetite and weight gain.

A phase II, randomized, double-blind, placebo-controlled, 22-day pilot study conducted in adult patients with advanced cancer showed that those treated with dronabinol (2.5 mg Δ9-THC b.i.d.) had improved chemosensory perception compared to those receiving placebo. The majority (73%) of dronabinol-treated patients reported an increased overall appreciation of food compared to those receiving placebo (30%). Similarly, most dronabinol-treated patients (64%) reported increased appetite, while the majority of placebo patients reported either decreased appetite (50%) or no change (20%). Total caloric intake per kilogram body weight did not significantly differ between treatment groups but increased in both groups compared to baseline. In addition, dronabinol-treated patients reported a higher protein intake as a proportion of total energy compared to placebo. The study authors minimized negative psychoactive effects by starting patients at a low dose (2.5 mg Δ9-THC once a day for three days) and gradually escalating the dose (up to a maximum of 7.5 mg dronabinol per day).

Reference information: https://www.canada.ca/en/health-canada/services/drugs-medication/cannabis/information-medical-practitioners/information-health-care-professionals-cannabis-cannabinoids.html#a4.1