Health Canada announced Tuesday it has approved Sativex, a marijuana-derived sublingual spray, for use as a pain reliever in patients suffering from advanced cancer. Sativex contains THC, the primary psychoactive ingredient in marijuana, as well as cannabidiol, a non-psychoactive compound.

The drug, manufactured by GW Pharmaceuticals, a British concern, and Bayer, can now be used by adult cancer patients who experience moderate to severe pain even while using the highest tolerated doses of opioid pain medications. Previously, its use in Canada had been limited to multiple sclerosis patients.

Like its use for MS, Sativex's use in cancer patients was approved under Health Canada's Notice of Compliance with Conditions policy, which means that while Sativex has demonstrated promising benefits, is of high quality, and possesses an acceptable safety profile, it still needs further study.

"Cannabinoids have an important role in treating complex cancer pain, particularly neuropathic pain, and demonstrate a positive effect with current treatment options," Dr. Lawrence Librach, the director of the Temmy Latner Centre for Palliative Care at Toronto's Mount Sinai Hospital, said in a Health Canada release.

"GW is delighted to receive Health Canada's regulatory approval for Sativex in the relief of cancer pain," said GW chairman Dr. Geoffrey Guy. "Sativex has been shown to provide important pain relief to the most high need patients with advanced cancer. We are pleased to be able to offer the prospect of an improved quality of life for people who previously had little such opportunity."