cannabis painkiller is approved

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By ANDRÉ PICARD
Wednesday, April 20, 2005 Page A1
PUBLIC HEALTH REPORTER
the globe and mail

Canada has become the first country in the world to approve the sale of a cannabis-based prescription painkiller.

Cannabis sativa L. has won approval from Health Canada regulators for treatment of a severe form of pain common among sufferers of multiple sclerosis, but it may also find favour with those with nerve pain related to conditions ranging from shingles to cancer.

The drug, marketed in Canada by Bayer HealthCare under the brand name Sativex, is sprayed under the tongue or inside the cheek.

While it contains the active ingredients that give pot smokers their buzz, including delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), users will not get stoned.

"These people are not feeling intoxicated by the drug, partly because the type of cannabinoids that have been isolated and purified work more specifically at the targeted pain receptors," said Dr. Virginia Devonshire, a neurologist at the University of British Columbia.

Patients who will be prescribed the drug will also be suffering from neuropathic pain, which is excruciating and can be provoked by movement, touch or temperature.

"It's like being plugged into an electric socket all the time," said Steve Walsh of Milton, Ont., who has endured neuropathic pain in his hand for five years since being diagnosed with MS.

He said that, at times, simple things like holding money in his hands "can be too much to take." None of the numerous painkillers he has tried to date provided any real relief, he said.

"There's a huge community of people with MS who are looking forward to this," Mr. Walsh said. "Personally, I would be tickled pink if it helped with the pain so I could do things like pick up my grandchild without suffering."

Sativex should be on the market in Canada before summer. The price of the drug has not yet been established.

While a number of drugs use synthesized forms of cannabis, this is the first to actually use marijuana extracts. The British drug company that developed Sativex, GW Pharmaceuticals, has been harvesting 40,000 pot plants in a secret location to produce the drug.

Dr. Allan Gordon, a neurologist and director of the Wasser Pain Management Centre at Mount Sinai Hospital in Toronto, said that while the drug is getting a lot of attention because it is derived from cannabis, the real story is that there is an "urgent need for additional treatment options in the field of neuropathic pain and MS."

It is estimated that more than half of the 50,000 Canadians who have multiple sclerosis suffer from chronic neuropathic pain, which is often described as freezing or burning sensations in the extremities. The condition has long puzzled researchers because it tends to be experienced in areas of the body that appear uninjured. It is also notoriously difficult to treat.

Many people with MS treat the pain by smoking marijuana, which is where scientists got the idea for developing a prescription drug derived from cannabis.

The problem with smoking marijuana is that the dose is hard to regulate and it can be difficult to get the drug legally. Mr. Walsh said that he tried smoking pot once to treat his pain, but he didn't like the experience. "I prefer to have something that's much more controlled and scientific," he said. "And, as an ex-smoker, I really don't want to get into the smoking habit again."

Sativex provides 2.7 milligrams of THC and 2.5 mg of CBD in a standardized dose with each spray.

Dr. Gordon said the spray is better than a pill because it "allows for flexible dosing and puts the patient in control of their pain. This is important since pain severity varies between different patients and even in the same patient at different times."

In clinical trials, Sativex provided more pain relief than a sugar pill, but its efficacy was not compared directly to other painkillers. In the clinical trials, side effects of the drug -- which included nausea, fatigue, dizziness and reactions at the site where it was sprayed -- were deemed to be mild.

Multiple sclerosis is a bedevilling disease of the brain, spinal cord and optic nerves that can affect muscle control, strength, balance, vision and sensation. For reasons that are unclear, the body's immune system malfunctions and starts attacking myelin, the protein coating that surrounds and protects nerve fibres.