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By Hempology | June 26, 2005

Health Canada has conditionally approved the first cannabis-derived prescription pain killer. Cannabis sativa extract ( Sativex ), an under-the-tongue spray, was approved in April for use as an adjunctive treatment for the symptom relief of neuropathic pain in patients with multiple sclerosis ( MS ). The drug should be available by June 21.

Figure. To meet demand for Sativex, GW Pharmaceuticals has increased production at its fortified greenhouses in the UK to 60 tonnes per year. Photo by: ABPI

The approval is conditional on the manufacturer, UK-based GW Phamaceuticals, conducting more clinical trials to confirm efficacy. Health Canada gave conditional approval because the drug fills an “unmet need,” said spokesperson Jirina Vlk.

About 160 patients with MS already obtain cannabis through the Marihuana Medical Access Program. The department won’t know whether Sativex will reduce enrolment in that program for about a year, said Vlk. “People may try [Sativex], then switch back [to smoking marijuana].”

Underlying the approval is an unpublished, phase III randomized controlled trial involving 66 patients with MS-related neuropathic pain; half took the drug and half placebo. The group receiving Sativex reported pain relief, less sleep disturbance and felt their condition had improved. Side effects included dizziness, nausea and fatigue.

“The data are okay, but not overwhelming,” says Dr. Paul O’Connor, director of the St. Michael’s Hospital MS Clinic — Canada’s largest, with 5000 patients. Results from previous trials, even one with 667 patients ( Lancet 2003;362:1517-26 ), have not produced consistent results, adds O’Connor.

In December, the UK refused to approve Sativex for the control of spasticity in patients with MS. The UK Medicines and Healthcare Products Regulatory Agency raised concerns about whether the results of a recent trial are statistically relevant. GW, which is developing a “portfolio of cannabis medicines” to treat people with diabetes, spinal cord injury, cancer pain and more, is appealing the decision.

O’Connors says he is “pleased patients have another option” that offers a more controlled dose than smoked cannabis.

Many patients also want to control the “high” they get from smoking. Health Canada’s statement of approval says that 70.5% of patients “experienced an adverse event classified as an ‘intoxication type reaction,’” including “feeling drunk.”

These adverse effects can be controlled by reducing the size or frequency of doses, says Dr. Tom Segerson of Bayer Canada, the division of GW in charge of distributing the drug here.

MAP posted-by: Richard Lake

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