Cannabis, often perceived as an illicit drug in the UK, has seen a significant shift in public perception since the rise of medicinal cannabis in November 2018. This change is due to an increased understanding of its potential therapeutic effects.

Medicinal cannabis, derived from the Cannabis sativa L. plant, has been utilised by humans for at least 12,000 years, serving various purposes from textile and rope production to treating medical conditions. Its compounds have been linked to numerous health benefits, sparking growing interest in its role in pain management, particularly for cancer patients.

Understanding the Endocannabinoid System

It was not until the 1980s that scientists began to comprehend the body’s endocannabinoid system (ECS) and how cannabis compounds interact with it. The ECS regulates several critical bodily functions, including mood, pain, sleep, and digestive health. Its potential role in managing cancer pain is a burgeoning area of research.

According to Macmillan Cancer Support, 3 million people in the UK are living with cancer, a number expected to rise to 5.3 million by 2040. On average, someone is diagnosed with cancer every 90 seconds. Despite advancements in cancer treatment, the disease remains prevalent and devastating, prompting patients to explore alternative pain management methods, including the use of THC, a compound in cannabis, for long-term pain relief.

THC: An Overview

Cannabis sativa contains over 110 different cannabinoid compounds, but THC (tetrahydrocannabinol) and CBD (cannabidiol) are the most well-known. THC is the primary psychoactive substance in cannabis, responsible for the ‘high’ associated with recreational use. In contrast, CBD, which has numerous potential health benefits, does not produce intoxicating effects. While hemp contains more CBD with minimal THC, most cannabis strains have higher THC levels.

THC interacts with the ECS by binding to neurotransmitters in the brain associated with pain, mood, and other sensations. It can induce feelings of euphoria and relaxation, increase appetite, alter time perception, and affect serotonin levels. Medicines containing THC may treat various conditions, including severe forms of epilepsy, multiple sclerosis-induced muscle stiffness and spasms, and chemotherapy-induced nausea, vomiting, and neuropathy.

Mechanisms of THC in Cancer Pain Management

Cancer pain arises as tumours press on nerves, bones, or organs, and release pain-causing chemicals. Cancer treatments like radiation, chemotherapy, and surgery also contribute to pain. Traditional pain management involves NSAIDs for mild to moderate pain and opioids for severe pain.

THC, when ingested, enters the bloodstream and is transported to the brain, triggering the release of dopamine, the “feel good” chemical. This process can temporarily relieve pain, improve mood, and promote relaxation.

Scientific Studies on THC for Cancer Pain

Research suggests THC may influence pain perception, making it a candidate for cancer pain management. One review indicated strong observational evidence that THC helps reduce pain in cancer patients. For example, patients already on opioids who took cannabis for three weeks reported improved pain scores. Another study noted decreased severe pain, reduced opioid use, and improved quality of life after six months of cannabis use.

A Canadian review found that THC-containing products could reduce pain for those unresponsive to opioids. However, reviewers cautioned that while beneficial effects were evident, many studies had limitations, necessitating further research to determine if THC could be a viable alternative or supplement to opioids.

Another review in the BMJ concluded that adding cannabinoids to opioid treatments did not significantly reduce pain in adults with advanced cancer. Additionally, THC may reduce chemotherapy-induced nausea and vomiting, showing mild effectiveness as an antiemetic.

Different Forms of THC for Cancer Pain

THC can be administered in various forms, including capsules, nasal or oral sprays, cannabis oil, tinctures, vaporisers, or edibles. Medicinal cannabis strains are bred to contain different levels of compounds, impacting their efficacy. The “entourage effect,” where terpenes enhance the potency of other compounds, is also a consideration.

Synthetic versions of THC, such as Dronabinol and Nabilone, exist, with Nabilone licensed in the UK to reduce vomiting in cancer patients. Sativex (nabiximols), a mouth spray, is licensed for multiple sclerosis treatment, and research is ongoing to assess its effectiveness for cancer-related symptoms.

Finding the most effective strain and method of administration requires individual experimentation and professional guidance. Patients are advised to consult healthcare professionals experienced in prescribing medicinal cannabis to determine the best treatment plan for their condition.

Legal and Regulatory Considerations

In the UK, the legal status of THC is complex. Recreational cannabis use remains illegal, with severe penalties for possession, production, or sale. However, medical cannabis containing THC can be prescribed under strict regulations since November 2018. Small amounts of THC are permitted in CBD oils, provided they do not exceed 0.2%.

Medical Cannabis: A New Avenue for Pain Relief?

While evidence suggests THC may benefit cancer pain treatment, more research is needed to determine its optimal use alongside or as an alternative to standard medications. The effects of medical cannabis vary between patients, necessitating a personalised approach to treatment.