As Canada prepares to legalize marijuana, the country's doctors have a lot of concerns about the nitty-gritty of the law and how it will impact their practice, and patients.

Jeff Blackmer, vice-president of medical professionalism for the Canadian Medical Association, said it doesn't matter whether physicians support legalization because that horse has left the barn, but "we need to figure out what we do when it is."

To that end, the CMA surveyed physicians on a broad range of practical issues, the results of which were presented at a meeting of the group's general council on Wednesday in Vancouver.

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Currently in Canada, marijuana can be prescribed and used for medicinal purposes, but possession for recreational use is still a criminal act (at least in theory.)

Physicians are divided on how pot should be regulated: 43 per cent believe there should be a single regulatory regime (meaning no distinction between medicinal and non-medicinal use), while 39 per cent back a dual regime.

"Will the new law mean we won't have to prescribe any more?" Dr. Blackmer asked. "That depends." Physicians were also asked where marijuana should be sold once it is legal: 56 per cent said in "existing non-health-care structure," meaning liquor stores; 47 per cent said in "legal storefronts" like dispensaries; 29 per cent in pharmacies ; and 16 per cent by mail. (The total exceeds 100 per cent because more than one choice was allowed.) Physicians were almost evenly divided on whether marijuana users should be able to grow their own.

Dr. Blackmer said the message in those choices is that "marijuana is recreational in nature."

The survey also asked at what age Canadians should be able to purchase legal marijuana: 45 per cent of physicians said over the age of 21, compared with 35 per cent who said age 18 or 19.

Dr. Blackmer said there is a scientific basis for having a higher legal age than cigarettes and alcohol because of marijuana's effect on the developing brain.

Where there was little disagreement was whether government should regulate THC levels in non-medicinal marijuana, with 72 per cent saying "yes."

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In a brief discussion of what the CMA should do next, conference delegates expressed a variety of concerns about legalization, ranging from the impacts of marijuana smoking on pregnancy through the need for more addiction treatment.

"Marijuana is here to stay," said Janice Wong, a Vancouver physician. "But we as the CMA must ensure government is aware of the ramifications of use of this psychoactive substance."

Pam Mansfield, a physician from Moncton, N.B., said one of the most concerning things is the levels of psychoactive substances like THC and CBD in marijuana are unregulated and unknown, so people don't know what's in their weed. Chris Milburn, a physician from Sydney, N.S., said doctors are too complacent about marijuana use by their patients.

"The more I learned about marijuana, the less I liked it," he said. "This is not a legitimate medical treatment."

But Ashley Miller of St. John's said she is not convinced that marijuana is as harmful as other recreational drugs, such as alcohol.

She said the role of physicians is to give patients the best information possible to reduce harm, and pleaded with the CMA to provide practical evidence that will aid in daily practice.

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Dr. Miller said a lot of her patients use marijuana and they have practical questions like: "What's safer: Vaporization vs. smoking vs. edibles."

Atul Kapur of Physicians for a Smoke-Free Canada said the reality is that "more high-school students toke than smoke" so, despite the fact that marijuana is being legalized, the CMA should advocate for strong public health campaigns, as they have done with tobacco.

"The goal of legislation is not to increase prevalence and use, it's to decrease harm," Dr. Kapur said.