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Sativex mouth spray sits on a book about medicinal uses of cannabis and cannabinoids.

Since the first cannabis-based drug was approved for use in Canada last year, doctors say the medication is catching on among people with multiple sclerosis and could be used for other types of pain.

Sativex is a mouth spray that delivers medicinal marijuana. The metered spray is administered under the tongue or inside the cheek. It's concentrated to offer maximum pain relief with minimal marijuana buzz.

Health Canada was the first drug regulator to approve the medication for people with multiple sclerosis who can't get relief from traditional drugs.

The spray treats neuropathic pain in MS – nerve pain that can be triggered by touch, temperature or movement and is often difficult to treat.

"It feels like its sort of boring through your bones," said Janet Liston of Ottawa. "It's like it's inside your bone."

Liston has been taking Sativex for six months, which is how long it has been available in Canada.

So far, a few hundred people worldwide have used Sativex in clinical trials. They report side-effects that include some respiratory infections. A feeling of mild intoxication or dizziness was the most common.

"The side-effects are a lot less than smoking marijuana," said Dr. Jock Murray, an MS specialist in Ottawa. "A lot of people surprisingly don't want to get high, they want to get relief from their pain."

Sativex will be tested in the U.S. for people with cancer. In Britain, it's being tried in the treatment of diabetic neuropathy.

Dr. Mark Ware is prescribing medicinal marijuana for a variety of conditions at his pain clinic in Montreal. The results so far are mixed but encouraging, he said.

"I think the potential for drugs like Sativex and the family of cannabinoid products which are inevitably to follow is incredibly wide."

One of the drawbacks of Sativex is that it costs about $500 a month. Provincial drugs plans don't cover it but some private insurance plans do.