Cannabis in cancer and palliative care (#117)
Although cannabis is still considered to have no accepted medical use and high potential for abuse (the definition of a Schedule I substance in the USA), an increasing number of states within the USA are allowing physicians to discuss and recommend the medicinal use of cannabis with patients despite the federal law. Cancer patients in particular may benefit from a number of health benefits attributed to the plant. Cannabis is the only available antiemetic that also stimulates appetite. Pre-clinical evidence suggests that cannabis may both prevent and treat chemotherapy-induced peripheral neuropathy. Placebo-controlled studies in patients with other neuropathic processes have demonstrated a clear benefit of cannabis. Trials investigating cannabinoid preparations in chemotherapy-induced peripheral neuropathy are ongoing. A small pharmacokinetic interaction study adding vaporized cannabis to sustained-released opiates demonstrated no significant change in opiate plasma levels over time and suggested a potential for a synergistic analgesic effect. Although not directly investigated as an endpoint, clinical trials have reported that patients receiving cannabis therapies experienced improved sleep. Among the cannabinoids (21-carbon terpenophenolic compounds), delta-9-tetrahydrocannabinol (THC) is the most prominent of the psychoactive components. Cannabidiol (CBD), on the other hand, is not psychoactive but has potent anti-inflammatory and analgesic effects. Cannabis dispensaries offer Cannabis sativa strains (more of an uplifting mind effect), Cannabis indica (more of a sedating body effect) and strains that are hybrids. Most dispensary “menus” list the percentage of THC, CBD and other biologically active cannabinoids in their available selections. Delivery systems offering an alternative to inhalation of combusted plant material are increasingly available. Patients should be cautioned that inhalation produces an effect that is more easily controlled in onset, depth and duration compared to oral ingestion of edible cannabis products or concentrated oil preparations to avoid unintentional unpleasant effects of excessive dosing. Cannabis use is otherwise a safe option for patients with cancer undergoing active treatment as well as those in end-of-life care. Despite pre-clinical evidence of antitumor activity of cannabinoids there are as yet no human studies investigating cannabis as an anticancer agent.