06/23/2014 12:37 EDT | Updated 08/23/2014 05:59 EDT

Medical marijuana's benefits debated

Many doctors remain ambivalent about prescribing medical marijuana for chronic pain, even though new federal rules allow patients in Canada to legally purchase dried cannabis with a doctor's prescription, a debate recently highlighted in a medical journal.

Monday's issue of the Canadian Medical Association Journal includes two pro/con-type commentaries: 

- New medical marijuana regulations: the coming storm

- Medicinal cannabis: Time to lighten up?

Dr. Meldon Kahan of the Substance Use Service at Toronto's Women's College Hospital and Dr. Anita Srivastava of St. Joseph's Health Centre and the University of Toronto argue physicians should advise some patients to quit smoking marijuana and refer them to treatment.

Kahan and Srivastava say the only clear indications for medical marijuana are neuropathic pain conditions (a type of chronic pain that affects the nerves) and spasticity from multiple sclerosis. Smoking cannabis is not recommended for common pain conditions such as fibromyalgia or lower back pain, they say.

Patients will ask doctors to prescribe cannabis for chronic pain but physicians need help to understand how to counsel people to know when and how to meet the requests.

"Smoked cannabis has short-term and long-term safety risks," the pair wrote. "Smoking cannabis has been associated with an increased risk of motor vehicle crashes, schizophrenia, mood disorders and addiction."

Prescriptions should state that the producer supply a strain with no more than nine per cent THC, the main psychoactive ingredient in cannabis, Kahan and Srivastava said.

For people who smoke marijuana, they suggested doctors advise:

- Don't light up daily.

- Don't mix it with alcohol or sedating drugs

- Don't drive after smoking up.

Dr. David Juurlink, an internist and head of the division of clinical pharmacology at the University of Toronto, said doctors shouldn't accede to every request for medical cannabis as if it were an "innocuous panacea" because it is not.

But doctors also shouldn't reject cannabis as a medicine out of hand just because it makes them feel uncomfortable, he said. Concerns about pot's safety and effectiveness shouldn't deter doctors from considering prescribing it in some cases, especially when opioid drugs like oxycodone carry heavier baggage in terms of toxicity.

"I'm trying to discourage physicians from the perception that drugs obtained at a pharmacy are necessarily better for an individual patient than cannabis, if a patient has reported benefits from its use," Juurlink said.

Instead Juurlink advocates for doctors to make decisions about prescribing cannabis when it is sometimes deemed the right thing to do, just as every other prescription decision is made after balancing the risks, benefits and patient-specific factors.