TORONTO -- Two medical groups weighed in Monday on the issue of medical marijuana, with the College of Family Physicians issuing guidelines to its members about which patients should and should not get prescriptions and the Arthritis Society calling for research to help doctors make those decisions.

College CEO Dr. Francine Lemire said the lack of research into cannabis has left many family doctors unsure about which patients could benefit from medical-grade weed and what dose should be prescribed.

"We're aware that there is demand out there by patients for dried cannabis for medical purposes," Lemire said from Ottawa. "We're aware of the relative lack of evidence, good solid evidence, for when to authorize or not to authorize (its use).

"And we felt that it was important for us to share what evidence there is with physicians and to support them in how to prescribe."

The college's recommendations, which are spelled out on the organization's website, say there is no research evidence supporting the use of cannabis for low back pain or fibromyalgia, but it could be considered for nerve-damage pain caused by such conditions as multiple sclerosis, metastatic cancer, shingles, diabetic neuropathy and severe injury.

But even in the case of such pain-causing conditions, doctors should consider using medical pot only after trying standard medications and therapies, including pharmaceutical cannabinoids, the document says.

"Authorizations for dried cannabis should only be considered for patients with neuropathic pain that has failed to respond to standard treatments."

Before prescribing, the college advises doctors to conduct a pain assessment, assess patients for anxiety and mood disorders, and screen them for existing substance use disorders.

The guidelines say patients under 25, those with substance abuse, cardiovascular or respiratory disease, and women who are pregnant, planning to become pregnant or breastfeeding should not be prescribed medical marijuana.

When its use is considered appropriate, the family doctor should regularly monitor the patient's response to treatment and discontinue authorization for its use if the smokable herb is clearly ineffective or causing harm, the college said.

College of Family Physicians: Guidelines on prescribing medical marijuana

In April, Health Canada changed its regulations to put prescribing of therapeutic marijuana in the hands of physicians, while supply of the dried herb was handed over solely to licensed growers for distribution to patients. Previously, patients with proven medical need had been allowed to grow or buy cannabis for personal use.

The shift in regulations put doctors across the country in an unenviable position: the onus for authorizing the use of medical pot was now their responsibility, yet many knew little about which conditions might be helped by the herb, what dose was appropriate and when it shouldn't be given to a particular patient, said Lemire.

Janet Yale, president and CEO of the Arthritis Society, said Health Canada records show that two-thirds of those licensed to buy or grow medical marijuana prior to the change in regulations were people with arthritis, and they likely continue to make up a large proportion of users.

"They live in pain, it's often untreated and they have historically suffered in silence, so we've made pain alleviation a real priority of our work, both in terms of our research agenda and our care agenda."

The society announced Monday that it will be funding patient trials into the safety and efficacy of cannabis in treating arthritis. It is also calling on other health charities, governments and licensed growers to fund research into the herb to help both patients and doctors make informed decisions about its use.

"We don't know its effectiveness in managing pain and fatigue caused by arthritis and other chronic disease. We just don't have good studies on that," said Yale, adding that researchers need to determine optimal dosages based on the type of disease, what form of delivery is best -- for instance, smoked, eaten or inhaled as a vapour -- and what potential interactions pot has with other medications.

Mary Ryan, 46, has ankylosing spondylitis, an inflammatory form of arthritis that affects the joints in the spine, which has left her with often excruciating pain.

"Medical cannabis has made it possible for me to get through the day, despite my arthritis pain," said the fast-food industry worker, who has been using marijuana twice daily, baked into a cookie eaten in the morning and inhaled through a vaporizer in the evening.

"When you live with chronic pain, you're desperate for any option that offers some relief."

On a scale of one to 10, Ryan typically ranked her pain at about a seven until she started using marijuana," she said from Hamilton, Ont. "And my pain will go down to two or three, depending on the day. And it keeps me moving."

But she'd like to know much more about the herbal drug, including whether there's any potential danger from ingesting it or inhaling it as a vapour. "I do worry that there's a lot we don't know about it, including its possible risks and benefits."

Dr. Mark Ware, a pain specialist at the McGill University Health Centre, lauded the Arthritis Society for its decision to fund research into medical cannabis.

"We do know that patients with arthritis have been saying that pain management is a huge problem for them," he said from Montreal. "The drugs that are available for managing arthritis pain are of limited efficacy in some cases and have side-effects that are quite dangerous in some cases.

"They're looking for options and alternatives, and medical cannabis has some promise in terms of a therapy."

Anti-inflammatory medications, including products that contain acetaminophen or naproxen, for example, can cause gastric bleeding and kidney or liver damage with long-term use, said Ware, who has prescribed therapeutic pot to a small number of his patients.

"So there's a clear need for a new class of medications to come forward that can optimally provide some control. Cannabinoids are not going to be a miracle drug for everybody, but they may be one more piece of equipment in the toolbox."

Lemire said family doctors can be faced with patients requesting marijuana whose medical conditions are often complex, but the research on which to base a prescription is inadequate or entirely lacking.

She said it's critical that more research into the safety and effectiveness of cannabis for various diseases be conducted to help physicians make educated decisions in order to best treat their patients.

"We feel that it's important for physicians not to authorize marijuana for medical purposes just because a patient is requesting it," Lemire said. "So there really is a need to review the condition of the patient, look at therapeutic approaches that have been used in the past and ... to be better informed about the evidence that is or isn't there in relation to marijuana prescribing."