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Health Canada approves Sativex®
for treatment of MS-related pain
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Medical Update Memo
April 19, 2005
Summary
On April 19, Health Canada approved Sativex®,
a cannabis-based drug for the treatment of MS-related pain.
The drug consists of various extracts from the cannabis plant.
It is administered via a spray into the mouth. The approval
is based on a clinical trial which took place in Britain in
2002. Canada is the first country to approve Sativex. Bayer
Canada will announce the cost and availability of the therapy
shortly. The Multiple Sclerosis Society of Canada welcomes
the approval of Sativex, which will provide people with MS
and their physicians another choice in treating pain, which
is a common symptom of the disease.
Details
Health Canada approval of Sativex on April 19 makes Canada
the first county in the world in which the cannabis-based
spray is available as a prescribed treatment for MS-related
pain. Sativex is sprayed under the tongue or on the inside
of the cheek from a dispenser that is programmed to deliver
a pre-selected dosage. It is described as a whole marijuana
plant extract. It includes two components of marijuana tetrahydrocannabinol
(THC) and cannabidiol.
Health Canada has approved Sativex with
conditions, under the Notice of Compliance with Conditions
(NOC/c) policy. This authorization reflects the promising nature
of the clinical evidence to be confirmed with further studies.
Products approved under Health Canada’s NOC/c policy,
have demonstrated promising benefit, are of high quality and
possess an acceptable safety profile based on a benefit/risk
assessment for the approved use.
Health Canada approval was based on the
results from a small, four-week clinical trial carried out
in Great Britain by GW Pharmaceuticals, the company that developed
Sativex. The study involved 66 people with MS at a research
centre in Britain. Participants had central neuropathic pain
because of MS. Half of the group received Sativex in a spray
dispenser and the other half received a sham (placebo) spray
in a similar dispenser.
The primary outcome measure was to measure
the effectiveness of Sativex in relieving central neuropathic
pain compared to placebo. Secondary measures included sleep
disturbance, participants’ perception of their condition
at the end of treatment and other quality of life assessments.
Study results and possible mechanism
of action
Participants in the Sativex group used fewer sprays per day
than did the placebo group. In addition, individuals in the
treated group reported they experienced pain relief, had less
sleep disturbance and felt their condition had improved.
There were more side effects in the Sativex-treated
group versus the placebo group. When combining data from this
and several other phase three clinical trials (total of 166
participants), the most common side effect of Sativex was dizziness
which occurred in 41.6% of treated participants versus 13%
of participants in the placebo group. There was also more nausea
in the treated group (10.2%) than in the placebo group (7.4%)
and more fatigue in the treated group (11.4%) versus the placebo
group (5.6%). Side effects tended to diminish overtime.
Cannabinoids is the name given to more than
60 related chemicals in the marijuana plant. Cannabinoids appear
to bind to receptor molecules on the surface of neurons in
the brain and spinal cord. Through a complex process, cannabinoids
appear to prevent neurons from becoming overactive, which leads
to the neuropathic pain sometimes experienced in MS. Neuropathic
pain results directly from damage to the nerves.
A number of clinical trials have been carried
out in the past five years to test the effectiveness and safety
of marijuana as a treatment for MS pain and spasticity. Some
studies used the smoked variety of marijuana, while others
used extracts of the plant delivered in various ways. The outcome
of the largest study, which looked at spasticity, was mixed
in that while those on active treatment did not have an objective
improvement as measured by a standardized scale, treated participants
reported improvements in walking speed, another measure of
spasticity, and symptoms of spasticity, muscle spasms, sleep
and pain.
Pain as a symptom of MS
Up to 80 percent of people with MS report some type of pain.
A recent study of pain at Dalhousie University involving
85 people with MS found that 53 percent of people with MS
experienced pain during the study period and that 17 percent
reported continuous pain. Of those reporting pain, 65 percent
took medication to control pain, with 90 percent reporting
that their pain could be controlled about half of the time.
Study participants who reported pain had poorer overall mental
health than people who were pain free or who had well-controlled
pain. There is a wide variety of pain associated with MS
from a range of causes: generalized pain, muscle spasms,
trigeminal neuralgia (shooting pain in the face), painful
sensations in the legs, feet and hands.
Background and status of marijuana as a
therapy in Canada
Marijuana’s role as a medication is complex and controversial.
It was used as a medication in the nineteen century but was
outlawed in most western countries in the early to mid twentieth
century. Recently in Canada, the federal government developed
a medicinal marijuana program, which allows people who meet
certain criteria to have permits to possess and grow marijuana.
MS is among the conditions for which a permit can be applied.
In some cases, Health Canada will provide marijuana to people
who hold permits. Details about how to apply for permits are
available at the Health Canada website.
Information is also available by calling the Health Canada
Cannabis Medical Access Office toll-free: 1-866-337-7705 or
613 954-6540.
It is not known if the approval of Sativex
will result in any changes to the Health Canada Marijuana Medical
Access Program. One issue that has arisen from the Health Canada
medical marijuana is that some physician organizations have
advised their members not to prescribe marijuana because of
the lack of information about optimum prescribing and potential
legal issues.
Other cannabis-based drugs are Marinol® (dronabinol)
and Cesamet® (nabilone). Both are synthetic
versions of THC in tablet form. They are used primarily by
people with cancer and AIDS to treat nausea related to certain
treatments and to stimulate the appetite.
Multiple Sclerosis Society of Canada
comment
The Multiple Sclerosis Society of Canada welcomes the approval
of Sativex, which will provide people with MS and their physicians
another choice in treating pain, which is a common symptom
of the disease. “Having available another way to manage
pain is encouraging news,” said Dr. William J. McIlroy,
national medical advisor.
ASK MS Information System
Code: 1.4.1.20.c2
Disclaimer
The Multiple Sclerosis Society of Canada is an independent,
voluntary health agency and does not approve, endorse or
recommend any specific product or therapy but provides
information to assist individuals in making their own decisions.
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