Cannabis based drugs: how will they be used in practice?

Who can prescribe?

Only specialists, and they will be expected to get approval from the chair of their hospital’s drug and therapeutics committee, or the medical director, on a named patient basis. GPs cannot prescribe.

What indications are included?

NHS England lists just two: children with rare forms of epilepsy and adults with nausea or vomiting caused by chemotherapy.1 “Very few people in England are likely to get a prescription for medical cannabis,” its guidance to patients says.2

What’s the evidence of benefit in these conditions?

Deb Pal, professor of paediatric epilepsy at the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, says that there is now good evidence from clinical trials that drugs based on cannabidiol are effective against two types of severe childhood epilepsy: Dravet syndrome and Lennox-Gastaut syndrome. Epidiolex, an oral solution of cannabidiol, has been licensed in the US for these two indications but not yet in Europe.

There is also good evidence that cannabinoids are effective in preventing nausea and vomiting induced by chemotherapy, say recommendations from the Royal College of Physicians. But more effective treatments are available, the RCP says, and cannabinoids should be used only by patients for whom standard treatments have failed.

Are any cannabis based drugs licensed?

Nabiximols (sold in the UK as Sativex) has been licensed since 2010 as a treatment for spasticity in multiple sclerosis. It contains cannabidiol and tetrahydrocannabinol (THC). But the National Institute for Health and Care Excellence says that it is not cost effective and should not be used in the NHS.

Who makes cannabis products?

Sativex and Epidiolex are made by the British company GW Pharmaceuticals, which is based in Cambridge. The company is supplied with cannabis by British Sugar, which grows it in a huge glasshouse at Wissington, near Downham Market in Norfolk.

What’s the evidence of harm?

Epidiolex trials showed side effects such as sleepiness, sedation, and lethargy; elevated liver enzymes; decreased appetite; diarrhoea; rash; fatigue, malaise, and weakness; insomnia, sleep disorder, and poor quality sleep; and infections.

Drugs that include THC have additional risks. The Royal College of Physicians lists psychosis, dependency, hallucination, and suicidal thoughts as possible side effects. The Royal College of Paediatrics and Child Health warns that THC may affect the developing brain and cause alterations to IQ and mental health. But much uncertainty remains because the legal status of cannabis has hitherto discouraged research.

Can private GPs prescribe these products?

No, because under amendments to the Misuse of Drugs Regulations only specialist medical practitioners, defined as those listed on the General Medical Council’s specialist register, are permitted to prescribe unlicensed cannabis based products. Anybody else who did so would be breaking the law.

What should GPs do if a patient asks for one of these products?

GPs should explain that they cannot prescribe the drugs. If they believe that the patient may meet the very narrow definitions laid down by NHS England, which include the lack of any licensed product that would meet the patient’s needs, they could refer the patient to a specialist.

Many people claim cannabis eases chronic pain. Are they excluded?

Yes. NHS England says that the evidence is insufficient to recommend cannabis based drugs for pain and that, lacking such evidence, they should not be prescribed. The Royal College Physicians says that there has been limited evidence of effectiveness in some studies of palliative care patients but not in others. Results of Sativex trials in this indication are equivocal. For long term neuropathic pain a Cochrane review in March 2018 concluded that potential benefits were outweighed by the risks,3 and a systematic review published in 2015 reached the same conclusion.4

A disappointing outcome?

For patients with chronic pain, yes,5 especially as the review by England’s chief medical officer that underpinned the recent law change cited among its “conclusive or substantial” evidence claims that cannabis based medicines were effective for chronic pain.6 Genevieve Edwards of the MS Society said, “The guidance published appears to ignore the clear evidence provided by the chief medical officer. For this change to have a real impact, everyone who could benefit must be given access in a safe, responsible, and fair way, with specialist doctors properly supported to make decisions around prescribing.”

Does the legal change go too far or not far enough?

Taken together, the change in the status of cannabis based medicines and the NHS England rules represent a minimalist position. Research into cannabis based drugs will become easier, but access to them will remain very limited. The Home Office has given with one hand, while NHS England has taken away with the other. But those who believe in evidence based medicine should not grumble, because the government has not buckled to political expedience.