Cannabis as a treatment for MS

Cannabis remains controversial, both in its status as an illegal drug and as a possible treatment for MS. This document discusses some of the historical and legal background to cannabis and cannabis-based medicines. It also provides an overview of current research into cannabis-based medicines as a treatment for MS.
Research into cannabis-based medicines for MS remains important because the way it works and its long-term effects are still not wholly understood. To date, no medicine derived from cannabis plant is licensed for use for any condition in the UK. However, Sativex, a cannabis-based medicine, is now available on a named patient basis in the UK - see our Sativex factsheet for further information. More research should strengthen the evidence base on which prescription of any cannabis-based medicine should be provided.

Background

Cannabis is one of the oldest plants in cultivation, and has been used to make textiles, fuel, paper, and rope as well as medicines. In addition it has been used recreationally as an intoxicant. Botanically, there are three recognised plants: cannabis sativa, cannabis indica, and cannabis ruderalis, only some of which have strong psychoactive properties. There are a number of common names for cannabis, including hemp, hashish, marijuana, skunk, weed, pot, grass and ganja.
Cannabis was legal in the UK until the Dangerous Drugs Act enacted in 1928, which outlawed private use but allowed medicinal use. The United Nations Single Convention on Narcotic Drugs 1961 did not recognise cannabis as having any medical or scientific benefit. UK law fully implemented this convention with the Misuse of Drugs Act 1971, which imposed penalties for possession and supply.

Legal status of cannabis

Cannabis is an illegal drug. Under the Misuse of Drugs Act 1971, illegal drugs are classed on a scale from Class A to Class C - most to least dangerous drugs. There is no clear protocol to state what effects a drug must have to warrant a specific classification. Drugs may be added to the Misuse of Drugs Act 1971, and reclassified within it, at any time. The law provides for some illegal drugs, such as such as morphine, which is derived from heroin, to be prescribed for some conditions. This is not the current legal position for cannabis, which is not recognised as having any medicinal value. The legal arrangements for providing Sativex are therefore exceptional.
Unless Sativex is prescribed, the penalties for possessing or using cannabis are still significant. In January 2004, the government reclassified cannabis from a Class B to a Class C drug. Class C drugs are illegal but lesser penalties apply than for Class A or Class B drugs, and these are: two years’ imprisonment and/or a fine for personal possession of cannabis, and five years’ imprisonment and/or a fine for possession with intent to supply. Supplying and dealing in Class C or Class B drugs carries a maximum penalty of 14 years’ imprisonment. Recent legal cases have indicated that the law makes no exception for people using or supplying cannabis to help relieve medical symptoms.
Several recent research studies have suggested that excessive use of recreational cannabis in young people may lead to long-term mental health problems. However, the Government has confirmed that cannabis will remain classified as a Class C drug.
The indications are, including its handling of Sativex to date, that cannabis-based medicines will be licensed so long as research trials prove that the medicines are effective.

Current research into cannabis-based medicines

Cannabis is known to work on parts of the brain known as cannabinoid receptors. However, how it works is not fully understood and is the subject of considerable research. Cannabis plants contain more than 60 different cannabinoids, which can affect these receptors. Only some cannabinoids are believed to help in MS.
Cannabis-based medicines may be based on the whole plant, or contain specific cannabinoids. Additionally, there are some medicines that are the chemical equivalent of some cannabinoids.
At the moment, two specific cannabinoids are believed to be of benefit in MS:

delta-9 tetrahydrocannabinol (THC) - known to be the part of cannabis that is psychoactive, that is, that gives a ‘high’, and is also thought to be responsible for some of the physical effects of cannabis, such as relaxation
cannabidiol (CBD) - a cannabinoid with few or no psychoactive properties, and some natural painkilling effect. It is thought to mitigate some of the unwanted effects of THC alone, such as feelings of drowsiness, weakness and cognitive impairment.

Drugs used in the research trials outlined below either contain one or both of these substances, or are based on the whole cannabis plant. It is worth remembering that the cannabis-based drugs used in these research trials have been quality-controlled and therefore may differ from ‘street’ cannabis.
The majority of research trials have focused on relieving symptoms of MS. However, one new trial, the CUPID trial, is looking to see whether cannabis might have a more important role in protecting the brain from damage by MS.

CAMS (Cannabis in MS) trial

The largest study of cannabis-based medicine as a treatment for MS was funded by a government agency, the Medical Research Council. Results from the trial were published in November 2003.
This was a randomised, controlled, double-blind trial which involved 660 participants at a number of sites around the UK. Participants were allocated to one of:

cannabis extract (Cannador) - capsules containing extract of cannabis plant, standardised to contain 2.5mg delta-tetrahydrocannabinol (THC)
dronabinol (Marinol) - synthetic delta-tetrahydrocannabinol (THC)
placebo - dummy treatment with no active ingredient

The trial investigated the effect of cannabis on various symptoms of MS, primarily on spasticity. A dose level was gradually built up over five weeks, treatment continued for a further eight weeks and was then tapered off over two weeks, with regular assessments for spasticity and mobility.
Results of this study were mixed. Researchers found that cannabis had no significant effect on the primary outcome measure of muscle spasticity as measured by the Ashworth scale. However, some improvement was shown on the time taken to complete a 10 metre walk, which was compared before and after treatment with cannabis.
Participants on the trial were asked to complete their own reports on symptoms. They reported improvements in spasticity, pain and sleep quality. This contrasts with the outcome measures the researchers used.
Importantly, participants on the trial experienced no significant adverse side-effects, and these drugs appeared to be very safe for use in the treatment of MS. There was little difference in the effect on symptoms between Cannador and dronabinol, suggesting that the whole plant or synthetic versions of cannabis may be equally effective. [1]
Extension trial: After the main 15 week trial had completed, all participants were given the option of continuing with their medication for a further twelve months. Around 80% of participants opted to continue.
Results from this trial suggested that cannabis-based medicine had some effect over the longer period of time on muscle spasticity, most notably in the group taking dronabinol, when compared with Cannador and placebo. However, only a small effect was seen.
In addition, there was some suggestion that dronabinol and Cannador might lessen some people’s increase in disability over a period of time. The investigators stressed that these results should be treated with caution, but the CUPID trial will investigate this possible effect more fully. [2]

Effect of cannabinoids on psychological factors in MS

This trial with a subgroup of people from the CAMS trial was fully funded by the read more