Abstract

Cannabinoids are chemicals derived naturally from the cannabis plant or are synthetically manufactured. They interact directly with cannabinoid receptors or share chemical similarity with endocannabinoids (or both). Within palliative medicine, cannabinoid receptors (CB1 and CB2) may modulate some cancer symptoms: appetite, chemotherapy-induced nausea and vomiting, and mood, pain and sleep disorders. Opioid and cannabinoid receptors have overlapping neuroanatomical receptor distribution, particularly at the dorsal horn, dorsal striatum and locus coeruleus. They have a favourable safety profile compared with opioids, and cannabis-based medicines help chronic pain. While cannabidiol (CBD) has anti-inflammatory properties, tetrahydrocannabinol (THC) is the psychoactive substance for issues such as mood and sleep. Nabiximols (Sativex), a CBD:THC combination, is Food and Drug Administration approved for some multiple sclerosis symptoms and epilepsy. There has been a swift societal evolution in attitudes about use of cannabis and cannabinoid medicines for chronic pain. In the USA, 33 states have now legalised prescription-based medical cannabis for several medical conditions; Canada has had legislation since 2001 authorising medical use. The European Union (EU) recently declared all EU citizens must have access to medical cannabis over the next 4 years. The integration into medicine and routine clinical use of cannabis is fraught with information gaps, regulatory issues and scarcity of research. Each patient should have a comprehensive assessment and risk–benefit discussion before any cannabis-based intervention to avoid possible complications such as hallucinations, psychosis and potential cardiac harm.