A new cannabis-based drug has been approved to relieve nerve pain in people with multiple sclerosis, Health Canada said Tuesday.

Sativex is a metred spray, administered under the tongue or inside the cheek. It's derived from extracts of the marijuana plant and is said to taste like peppermint.

Canada is the first country to approve its use, although the drug company Savitex must first do more clinical trials to confirm the effectiveness of the drug.

GW Pharmaceuticals developed the drug, which will be marketed in Canada by Bayer.

"Effective pain control and management are extremely important in a disease like MS," pain expert Dr. Allan Gordon said in a release issued by the companies.

"The approval of Sativex in Canada reflects the urgent need for additional treatment options in the field of neuropathic pain in MS," added Gordon, a neurologist and director of the Wasser Pain Management Centre at Toronto's Mount Sinai Hospital.

Health Canada confirmed the approval to CBC News.

About 50,000 Canadians have MS. Half of them are estimated to suffer from nerve pain, for which there are few treatments.

Neuropathic or nerve pain can be triggered by touch, temperature or movement.

The companies say Sativex contains tetrahydrocannabinol, or THC, and cannabidiol as its main components.

The drug works by stimulating cannabinoid receptors in the central nervous system, which in turn mediate pain.

During clinical trials, side-effects included nausea, fatigue, dizziness and reactions at the application site. Side-effects were usually mild or moderate in severity and eased at lower doses.