EducationA detailed guide on THC for cancer pain

A detailed guide on THC for cancer pain

8 min read

Lucy MacKinnon

A detailed guide on THC for cancer pain


We have all heard about cannabis, right?

Most often thought of (unfortunately, still) as an illicit drug here in the UK, but with the rise of medicinal cannabis starting in November 2018, public perception of the plant has seen a huge shift thanks to an increased understanding of the potential therapeutic effects it offers.

Medical cannabis, or cannabis sativa L., has been cultivated by humans for at least, 12000 years, and has many uses from textiles, clothing and rope production, to treatment of medical conditions. It offers numerous potential health benefits, and its compounds have been linked to a wide range of positive health outcomes.

Yet it was only in the 1980s that scientists began to truly understand the body’s complex endocannabinoid system (ECS) and how cannabis compounds interact with it. The ECS is responsible for regulating a number of critical bodily functions such as mood, pain, sleep and digestive health and a growing area of study is its role in the management of cancer pain.

According to Macmillan Cancer Support, there are 3 million people in the UK living with cancer, and this is expected to rise to 5.3 million by 2040. On average, someone is diagnosed with cancer every 90 seconds.

While there have been huge advances in cancer treatment, it’s still a hugely prevalent and devastatingly destructive disease. Inevitably, patients have looked at alternative ways of managing pain with cannabis compounds, specifically THC, which potentially has a role to play in long-term pain relief.

What is THC?

Cannabis Sativa is an extremely versatile, hardy plant containing more than 110 different cannabinoid compounds, but the two that people most frequently talk about are THC and CBD. THC (tetrahydrocannabinol) is the most active substance in the cannabis plant and gives the characteristic ‘high’ that it’s commonly associated with recreational cannabis consumption. CBD (cannabidiol) is the second most active compound with a range of potential beneficial effects on health and wellbeing, but it reacts differently with the body and has no intoxicating effect. They are both found in cannabis and hemp, but hemp contains more CBD with minimal THC, while most cannabis cultivars contains more THC.

THC works with the body’s ECS. It binds with neurotransmitters in the brain which are most associated with pain, mood, and other feelings. It can make patients feel euphoric and relaxed. THC can also increase appetite, create a heightened (or dulled) perception of time and the senses, and alter levels of serotonin in the brain. Medicines containing cannabinoids including THC may be useful in treating a range of health conditions – rare and severe forms of epilepsy, muscle stiffness and spasms caused by multiple sclerosis and nausea, vomiting and neuropathy caused by chemotherapy.

Mechanisms of action of THC in cancer pain management

As tumours grow, they can press on nerves, bones, or organs, causing the patient pain. Tumours can also release chemicals which cause pain, while the treatments for cancer itself – radiation, chemotherapy and surgery – can also lead to pain. Traditional cancer pain management relies on the use of non-steroidal anti-inflammatory drugs (NSAIDs) for mild to moderate pain and opioids for moderate to severe pain.

When a person takes THC, it passes into the blood, where it’s transported to the brain. THC triggers your body to release large amounts of dopamine, colloquially known as the “feel good” chemical. This in turn can temporarily relieve pain, improve mood, and promote relaxation.

Scientific studies on THC for cancer pain

Given that THC has the potential ability to influence the body’s pain perception, it has the potential application for cancer pain management. One review concluded there is strong observational evidence that THC aids pain reduction in cancer patients. 

Indeed, in one of the trials it reviewed, patients who were already taking opioids who took cannabis for three weeks reported an improved pain score. Another study in the review showed decreased severe pain, decreased opioid use, and improved quality of life in patients who took it for six months.

A Canadian review of cannabis administration to manage cancer pain found some studies that showed evidence THC-containing products could help reduce pain and be beneficial to those sufferers who didn’t respond well to opioids. Another study in the same review concluded that significant pain relief was achieved with low doses. 

However, the reviewers cautioned that while there was evidence showing beneficial effects, many of the studies were limited in their scope and further research was required to establish whether THC could be taken as an opiate alternative or in addition to them.

Similarly, a review in the BMJ concluded that the addition of cannabinoids to opioid treatments did not reduce pain in adults with advanced cancer.

There is also some scientific evidence that THC may reduce nausea and vomiting in patients undergoing chemotherapy. Researchers tested THC as an antiemetic and found it was mildly effective in preventing vomiting.

Different forms of THC for cancer pain

THC can be administered in several ways. It can come as a capsule which is swallowed, as a nasal spray or oral spray, as cannabis oil or as a tincture placed under the tongue. THC can also be taken by inhaling it in a vaporiser or adding it to food.

As we said, medical cannabis contains hundreds of different compounds which have varying effects. Different strains have been bred to contain different levels of certain compounds, so certain strains will be more beneficial for some patients than others. While they also contain THC and CBD, the levels of those compounds in each strain will vary, which will impact efficacy.

As well as cannabinoids, the concentration of terpenes in medicinal cannabis is a consideration as this can have an “entourage effect”, increasing the potency of the other compounds.

Synthetic versions of THC called Dronabinol and Nabilone exist, although only Nabilone is currently available as a licensed medicinal product and has been prescribed to reduce vomiting in cancer patients. Sativex (nabiximols), a liquid which is sprayed in the mouth, is licensed in the UK to treat multiple sclerosis patients. Research is underway to see if it is effective for cancer-related symptoms.

Ultimately, discovering which strain works well is about the individual needs of each patient. It may take some experimentation to discover which strain you tolerate best and which provides the most relief. If you would like to learn more about medicinal cannabis, and how it may offer therapeutic benefits for your unique circumstances, then it is always advised that you reach out to a doctor or healthcare professional that has experience in prescribing medicinal cannabis. Only they will be able to advise you on the best treatment plan for your condition.

Legal and regulatory considerations

The law surrounding THC administration in the UK remains complex. It is illegal to consume, possess, produce, or sell cannabis recreationally. People caught in possession can be jailed for up to five years, while those who supply or produce face up to 14 years in prison. It is still classed as a Class B illegal substance.

Small amounts of THC can be legally present in CBD oils, but if the amount exceeds 0.2% this will render the product illegal.

Changes to the Misuse of Drugs Regulations were passed in November 2018 which made it legal for British patients to be prescribed medical cannabis without the approval of an oversight committee. There are strict controls in place over its use and it can only be prescribed by a medical professional under certain circumstances.

Medical cannabis – a new kind of pain relief?

While there is mounting evidence to suggest THC is beneficial in the treatment of cancer pain, further research is required to discover whether it works optimally as additional pain relief alongside standard medications or whether it is suitable as a standalone treatment. What is clear is that the effects of medical cannabis for cancer pain and its associated benefits will vary from patient to patient, which is why a highly personalised approach is required.

Accessing medical cannabis can be challenging due to the stigma surrounding it. However, Releaf makes it simple with our tailored monthly packages, specialist consultations for medical cannabis, and a unique medical cannabis card for protection, all based on your cannabis prescription

It is important to seek medical advice before starting any new treatments. The patient advisors at Releaf are available to provide expert advice and support. Alternatively, click here to book a consultation with one of our specialist doctors.

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With five years of journalism and healthcare content creation under her belt, Lucy strives to improve medical cannabis awareness and access in the UK by producing high quality, credible content.

Our articles are written by experts and reviewed by medical professionals or compliance specialists. Adhering to stringent sourcing guidelines, we reference peer-reviewed studies and scholarly research. View our editorial policy.

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Further reading

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Medical cannabis on holiday: The basics

Here at Releaf we understand that holidays should be about relaxation, but travelling with medical cannabis sounds like a stressful voyage. We’re doing what we can to absorb that stress so that you can soak up the sun, and so, we’ve designed a series of articles to cover the subject: medical cannabis on holiday. 

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How long does it take to feel the effects of THC oil?

The time it takes for you to feel the effects of THC depends on the methods of administration as well as your own physiology. Fortunately, there are fast and slow-acting options, as well as ways to take low or high doses in order to facilitate control over the way your body reacts to your medicine.

Editorial Team