The clinical effectiveness of medical cannabis for symptom control in adult palliative care patients is unclear, due to a lack of quality and quantity of evidence; this lack of evidence applies to the cannabis plant, its extracts and synthetic cannabinoids. From a systematic review of nine randomized controlled trials, low quality evidence suggests that in patients with HIV, dronabinol (a synthetic cannabinoid) may be more effective than placebo for appetite and weight gain, at the expense of increased risk of psychiatric adverse effects. In patients with cancer, dronabinol may be less effective than megestrol for improvement in appetite, weight gain and health-related quality of life, and may increase risk of withdrawal due to adverse events as compared to megestrol. Similarly, in patients with HIV, dronabinol may be less effective than megestrol for weight gain. Two evidence-based guidelines address the use of medical cannabis in a palliative care setting. The first evidence-based guideline explicitly recommends against the use of medical cannabis as a first or second line option for palliative cancer pain. The guideline suggests that it could be considered in the case of refractory symptoms and with careful consideration of potential risks. The second evidence-based guideline similarly recommends that medical cannabis only be used in the palliative care setting when other treatments have failed, and after consideration of the potential for adverse events and drug interactions.