Medical cannabis for pain in the UK: what the NHS and NICE say

The NHS describes medical cannabis as a broad term for any sort of cannabis-based medicine used to relieve symptoms. This covers very different things: licensed or specially prescribed medicines made to a pharmaceutical standard, products sold online whose quality and content is not known, and CBD oils sold as food supplements.

The NHS explains that CBD (cannabidiol) will not get you high, because it does not contain THC (tetrahydrocannabinol), the chemical in cannabis that does. It says products that claim to be medical cannabis, such as CBD oil or hemp oil, are available legally as food supplements from health stores but there is no guarantee they are of good quality or provide any health benefits.

The NHS says there is some evidence medical cannabis can help certain types of long-term pain, but that this evidence is not yet strong enough to recommend it for pain relief, although in some cases it may be prescribed for pain as part of a clinical trial.

NICE's guideline on cannabis-based medicinal products looked at the evidence for chronic pain, severe epilepsy, spasticity from MS and chemotherapy-related nausea and vomiting. NICE's public information says it was not able to recommend any cannabis-based medicines for pain, or for most types of epilepsy, and that more research is needed. It says adults with MS can be offered a trial of a cannabis-based mouth spray for spasticity, and that nabilone may be an option with other anti-sickness drugs during chemotherapy.

The NHS says a prescription for medical cannabis would only be given when it was believed to be in your best interests and when other treatments had not worked or were not suitable. The specialist will discuss all the other treatment options first. It adds that if the listed conditions do not apply to you, you should not ask a GP for a referral for medical cannabis.

NICE's public information says a specialist doctor will need to prescribe cannabis-based medicines to start with, and should give clear information about benefits and harms, any risk of dependence and how it may affect you. If you are already taking a cannabis product that has not been recommended, you and your doctor can work out the best time to stop.

The NHS says the risks of cannabis products containing THC are not currently clear, which is why clinical trials are needed. The risks it lists include psychosis, since there is evidence that regular cannabis use in some people can increase the risk of developing a psychotic illness such as schizophrenia, and dependency, although it says this risk is probably small when use is controlled and monitored by a specialist. The more THC a product contains, the greater these risks are.

Possible side effects listed by the NHS include decreased appetite, diarrhoea, feeling sick, weakness, a behavioural or mood change, dizziness, feeling very tired, feeling high, hallucinations and suicidal thoughts. CBD and THC can affect how other medicines work, and CBD can affect the liver so doctors would need to monitor you regularly. Side effects can be reported through the Yellow Card Scheme.

The NHS warns that many cannabis-based products available to buy online are of unknown quality and content, and that it is likely most of these products, even those called CBD oils, will be illegal to possess or supply, with a good chance they contain THC and may not be safe. Cannabis bought illegally off the street, where the quality, ingredients and strength are not known, is described as the most dangerous form to use.

The NHS also gives advice on proving you have a prescription if you travel, such as keeping medicine in its original packaging, a copy of the prescription and a letter from the prescribing doctor. Some people with chronic pain use private clinics that prescribe cannabis-based medicines. The NHS pages used here do not evaluate private prescribing, so anyone considering it should check the clinic is regulated, understand the cost and tell their GP.

The NHS describes medical cannabis as likely to benefit only a very small number of patients and as something considered when other treatments have not helped or are not suitable. The other treatment options for long-term pain are not described in the pages used here, so a GP or pain clinic can explain what is available for your type of pain.

People with chronic pain who have not found enough relief can ask their GP about referral to a pain management service, which offers a coordinated approach.

Speak to a GP if pain is persistent or affecting daily life. Anyone using cannabis products who develops confusion, hallucinations, paranoia, severe mood change or thoughts of self-harm should get urgent help from NHS 111, a GP or 999.

People taking other medicines should check interactions with a pharmacist or specialist before taking any cannabis-based product, as the NHS says CBD and THC can affect how other medicines work.

On the NHS, cannabis-based medicines are prescribed by specialists for the specific conditions described. For pain, they are not routinely available. Access to private prescribing exists in the UK, with costs borne by the patient.

Whatever the route, it is worth asking the prescriber what evidence supports the treatment for your type of pain, how benefit will be judged, how long a trial will last and what monitoring is planned.