It is estimated that 15 percent of people with MS use the drug hemp (cannabis or marijuana) on a regular basis. Although cannabis does not modify the disease process of MS, many people believe that the drug relieves their symptoms such as stress, sleep disorders, muscle spasms and pain more effectively than any conventional medicine and they are willing to break the law for their belief. Does this relatively high prevalence of cannabis use among people with MS mean that they have found 'the most valuable medicine we possess' as the famous 19th century physician, Dr J Russell Reynolds, said? Or are they vulnerable people who are victims of a hoax?
An ancient painkiller banned
Cannabis has been known as an analgesic agent for more than 4,000 years and belongs to the plant-drug group that, along with coca and opium, remains in use today. The plant was introduced into European medicine from India in 1842 to relieve pain, muscle spasms, convulsions of tetanus, rheumatism and epilepsy and was used medicinally as tinctura cannabis well into the 20th century. But because of quality control issues and political pressure in a world of growing drug abuse, cannabis was eliminated from the modern Western pharmacopoeia in 1961 when the United Nations Single Convention on Narcotic Drugs decided that cannabis had no medical or scientific benefit. No wonder - nobody knew at that time that the human body possesses its own endocannabinoid system with analgesic properties!
How does this endocannabinoid system work?
Tetrahydrocannabinol (THC) is largely responsible for the psychopharmacological properties and physical effects of cannabis. Interest in therapeutic uses for cannabinoids increased after the discovery of a human cannabinoid receptor (CB1), anandamide. Anandamide, naturally present particularly in the brain, is a neurotransmitter that targets the same brain structures as THC, the active ingredient in cannabis. Neurotransmitters are the chemical messengers of the brain. They work by transporting electrical signals between nerve cells. These signals cause changes in the sensations and emotions that we experience.
Additionally, CB1 receptors are found on pain pathways in the brain and spinal cord and also outside the central nervous system, and are thought to be involved in cannabinoid-induced analgesia (perceived pain reduction). However, the precise way in which cannabinoids produce analgesic effects at these sites remains unclear.
Cannabis studies
Following a recent trial, Sativex®, a cannabis extract which is sprayed in the mouth and contains equal amounts of THC and cannabidiol (another cannabinoid of the hemp plant) received approval in 2005 in Canada for the symptomatic relief of neurogenic pain in MS. In the trial, 66 people with MS experiencing painful spasms or dysesthetic pain (uncomfortable sensations such as pins and needles, burning pain, numbness or tightness) received either a cannabis-based medicine or placebo in the form of a mouth spray. Pain and sleep disturbances were recorded on a visual analogue scale. The treatment group reported a reduction of 2.4 on an 11-point pain scale (0-10), while the placebo group report a reduction of 1.4 points. The participants also reported a similar improvement in sleep (Rog DJ et al., Neurology 2005).
The analgesic properties of THC were also examined in a 2004 Danish study where 24 participants with MS who had received THC reported an improved quality of life and felt a reduction of their pain (Svendsen KB, BMJ 2004).
The participants of the large CAMS study in the UK who took cannabis capsules reported an improvement in spasticity and sleep, and also in pain. Finally a recently published Canadian meta-analysis of cannabis-based treatments for neurogenic and MS-related pain involving 298 patients concluded that cannabinoids were effective in treating neurogenic pain in MS. This review however, was based on a small number of trials and subjects (Iskedijan M, Curr Med Res Opin 2007).
In the future - overcoming the barrier of psychoactive side effects
Alongside the positive effects on pain symptoms reported in these different studies, it was also noted that the use of cannabis caused side effects, especially at higher doses, such as weakness, dry mouth, dizziness, mental clouding, short-term memory impairment and space-time distortions.
These side effects may explain the high drop-out rates in some studies. Recent research studies have also suggested that excessive use of recreational cannabis in young people may lead to mental health problems. Finally, the double blind character of these studies has also been questioned because cannabis is psychoactive and tends to make people feel 'high.' This means that people taking the active drug during a clinical trial usually become aware of it, thus, 'unblinding' the study and possibly biasing results. This particular aspect has led some to think that the effects are only imaginary. Some practitioners believe that for people who can tolerate the drug, cannabinoids represent a valuable alternative when pain has not responded to other drugs.
In the future, the goal of new therapy development that focuses on the CB1 receptor should weigh the risk-benefit ratio of the treatment, because the current relationship between symptom relief and the psychoactivity of cannabis is unbalanced. Cannabis continues to be a controversial treatment in MS and remains illegal in many countries.
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