Toronto -- Multiple Sclerosis (MS) patients with neuropathic pain for whom conventional treatments have failed now have an alternative to Health Canada's controversial medical marijuana program.
Canada has become the first country to approve the cannabis-based drug, Sativex, for the treatment of MS-related pain. That approval means the drug has demonstrated promising benefit, is of high quality and possesses an acceptable safety profile based on a benefit-risk assessment. Further studies will now be required to confirm the promising nature of the clinical evidence its approval is based upon.
Despite revised medical access regulations that in July 2001 legalized the use of marijuana for MS patients with severe pain and/or persistent muscle spasms, the drug's role as a medication has remained complex. Many physicians have been advised not to prescribe marijuana because of the lack of information about optimum prescribing and potential legal issues.
Dr. William McIlroy, the national medical adviser for the MS Society of Canada, said physicians at his own hospital made the decision a year ago not to prescribe marijuana until more objective evidence becomes available.
Sativex, on the other hand, is "good news for the Canadian MS community" and "will likely be welcomed by the many people with MS, whose quality of life has been further compromised with neuropathic pain," he said in a statement on behalf of the society.
In an interview, Dr. McIlroy also said that he is "positive in a guarded sort of way" about the drug, explaining that "evidence to date in support of it is relatively limited."
Health Canada's approval of Sativex was based on the results of a four-week clinical trial involving 66 patients with MS-related neuropathic pain that was carried out in Great Britain, in which half received Sativex and the other half received a placebo.
The results showed participants used Sativex (prescribed on an as-needed basis) less often compared to the controls using placebo. Sativex is administered via a spray into the mouth, which is well suited to the variable nature of neuropathic pain experienced by people with MS. Placebo patients in the study also used a spray.
The Sativex group reported pain relief, less sleep disturbance and felt their condition had improved. But they also experienced more dizziness, nausea and fatigue.
Dr. Allan Gordon, a neurologist and director of the Wasser Pain Management Centre at Mount Sinai Hospital here, said he believes Sativex will become another valuable treatment option for MS-related pain. "It's not going to be the only part of the treatment for chronic pain, but it's going to be an important part."
Although many doctors aren't familiar with prescribing cannabinoids for pain, Dr. Gordon said "you have to go to the paradigm we have for treating pain, which is to take a history carefully, examine a patient carefully (and) do a history of alcohol abuse or substance abuse."
Several studies completed at Dr. Gordon's pain and MS clinics found 20% to 30% of respondents had reported using marijuana actively or in the past and found it had some benefit.
"It might be useful to try to get use of (marijuana) that doesn't have the stigma with it," he said, noting it was used as medicine in the 19th century until it was outlawed in the early to middle 20th century.
Neuropathic Pain Conditions
Like Dr. McIlroy, Dr. Gordon said more robust evidence is required to determine the efficacy of Sativex for MS-related pain. However, based on evidence to date, he said he would also like to see Sativex tested in other kinds of neuropathic pain conditions, such as stroke or spinal cord injury.
Moreover, he said Sativex provides an opportunity for MS patients who don't want to use medical marijuana but still want to see if a derivative of the compound works for them.
Sativex isolates the cannabinoid components, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), representing only two of the more than 60 related chemicals that make up the marijuana plant. It is believed that THC helps patients with pain while CBD has a neurological effect, and that isolating these two cannabinoids will enable patients to eliminate many of the side-effects that are associated with the use of medical marijuana.
"If you smoke marijuana you've had exposure to some very different effects," Dr. Gordon said, adding it is unlikely that patients taking Sativex will experience the high associated with marijuana use.
Note: Sativex approved for MS patients.
Source: Medical Post (Canada)
Author: David Hodges
Published: May 17, 2005 Volume 41 Issue 19
Copyright: 2005 The Medical Post