Phytocannabinoids as Chemotherapy Adjuncts—A Review for Users

Cancer, one of the leading causes of death worldwide, is on the rise. The high toxicity of conventional chemotherapy, often applied as drug cocktails, and the development of resistance limit the use of antineoplastic drugs and reduce the quality of life. With easier access, a growing number of patients are using cannabis (cannabinoids) for alleviation of their symptoms, and in the hope of improving survival. This article summarizes results observed with combinations of phytocannabinoids and standard chemotherapeutic agents in animal tumour models and in patients. It is limited to approved phytocannabinoids. Preliminary preclinical data suggest that conventional antineoplastic agents combined with cannabinoids exert enhanced anti-cancer effects, reduce resistance development and improve survival. Corresponding experiences with patients are still very limited and only concern a few patients with glioblastoma and pancreatic cancer. Benefits of combinations containing cannabinoids have also been reported for chemotherapy-induced nausea and vomiting, loss of appetite (dronabinol), and chemotherapy-induced peripheral neuropathic pain and anxiety (cannabidiol). In addition, phytocannabinoids, particularly cannabidiol, may play a role in protecting organs such as the heart, lungs or kidneys from chemotherapy-related toxicity. Although the results are promising, more research is needed to ensure whether the benefits of adjuvant cannabinoids outweigh the potential risks.