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Would you benefit from medical cannabis?

The use of cannabis in the NHS is a polarising topic that raises many questions amongst clinicians and the British public alike. High profile cases such as Billy Caldwell, a young boy with severe epilepsy whose mother used medical cannabis from the US to alleviate his symptoms, resulted in a change of UK law to allow prescription of medical cannabis in specific instances. Although the law has changed it is very difficult for patients including Billy Caldwell to get access to cannabis-based drugs.


Current guidelines state that only specialist doctors can prescribe cannabis-based products for patients with rare forms of severe childhood epilepsy and patients suffering from chemotherapy-induced nausea and vomiting. In both instances, there must be no effective licensed product for a specific condition. Due to these stipulations, many people are unable to access the drugs.


What is medical cannabis?


Medical cannabis termed “cannabis-based product for medicine” (CBPM) by NHS England must fulfil three requirements:


1. The product contains cannabis, cannabis resin or a cannabinol derivative

2. The product is for medicinal use in humans

3. The product is regulated as a medicinal product or an ingredient of a medicinal product.


Cannabis comes from the cannabis plant and contains over 100 components including cannabinoids, terpenes and flavonoids. The most studied chemicals are cannabidiol (CBD) and tetrahydrocannabinol (THC). THC is associated with recreational highs, while CBD is not. The ratio of THC to CBD is important as CBD can cause more harmful effects of THC such as psychosis. The illicit form of cannabis usually comes as dried leaves which are smoked. Studies (Lancet) have shown that illicit cannabis has similar effects on the body as THC by increasing the odds of developing a psychotic disorder, therefore prescription of CBPMs must be controlled. Unlike the illicit form, cannabis compounds in CBPMs are synthesised creating products that are chemically identical or mimic the effects of cannabis.


Who can prescribe it?


Currently, only specialist doctors can prescribe CBPMs. Sativex (nabiximols) is a licensed drug currently used for spasticity due to multiple sclerosis and is the first CBPM to be licensed in the UK. It is sprayed under the tongue and given to those with moderate to severe multiple sclerosis spasticity symptoms however it is not recommended for prescription by NICE as it is very expensive. Another license drug is Nabilone, a synthetic cannabinoid which has been available for decades and is used as an add on treatment for adults with chemotherapy-induced nausea and vomiting after failing to respond to conventional licensed treatments.


What evidence is there for the use of medical cannabis?


There have been a number of trials of varying quality demonstrating the effects of cannabis for different conditions. Cannabinoids have been shown to possibly reduce seizure frequency by more than 50% in half of the patients when used as add on therapy in drug-resistant epilepsy in children and young people. There are currently unknown benefits in adults with epilepsy and Dame Sally Davies found “no or insufficient evidence regarding cannabinoid” use in other forms of epilepsy. Using THC for neuropathic pain (shooting or burning pain) is promising but there is little data for the use of CBD. The British Medical Journal (BMJ) suggests there is benefit in using CBPM for arthritis and cancer pain while Dame Sally Davies found “conclusive or substantial evidence for the treatment of chronic pain”. Many trials have shown a benefit in using CBPMs for chemotherapy-associated nausea and vomiting in comparison to a placebo, however, CBPMs have not shown to be more effective than standard treatments.


The NICE guideline recommends that GP should be able to prescribe CBPMs once the drugs have been started by specialists in expert centres as part of shared care agreements. Nabilone is the only CBPM that NICE recommends. Other CBPMs for other conditions are not recommended by NICE due to lack of evidence and lack of cost-effectiveness. Therefore, NICE believes the other CBPMs should only be used as part of trials. These guidelines mean that many patients and families have been left disappointed and NICE do apologise for this but state that high-quality research is required for patients with treatment-resistant epilepsy, spasticity, fibromyalgia and chronic pain management.


What are the risks of medical cannabis?


There is a lack of long-term safety data however the short-term risks are believed to be dizziness, euphoria, drowsiness, dry mouth, confusion, disorientation, somnolence, balance problems and fatigue. In the long-term possible risks are neuropsychiatric effects as the current data suggests there is a causal link between cannabis use and psychosis. There is also the possibility of mental health issues such as depression and anxiety disorders.


While there is relatively strong data for the use of CBPMs in rare forms of severe childhood epilepsy there is a lack of strong data on how effective CBPMs are for other conditions as well as a lack of research on the short-term and long-term side effects of CBPM use. This means, unfortunately, there are limitations on safely prescribing the CBPMs to patients. Cannabis-based product medicines seem to be a promising area and will hopefully after further research they will be used to improve the quality of life of many people.


Korede Salami - Purpose Print Team


Disclaimer: Information in our blogs are as accurate and a comprehensive as possible. This is general advice and should not be used as a substitute for the individual advice readers might receive from consulting their own doctor. For other medical professionals reading, it is advised to use your own clinical judgement when interpreting the information and deciding how to best apply this to the treatment of their patients. Please see our terms and conditions page for further information on this.

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