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ORLANDO – An essential element in prescribing medical marijuana responsibly is to insist that the patient must demonstrate improved functional status to be allowed to continue with the therapy, one expert has advised.
"Functional status is really the major issue. If cannabis is going to be used as a medicine, we have to see improvement in function: return to work, improvement in daily activities, engagement in society. I tell patients, ‘If this drug is really helping you, then show me. Show me that you can come off this other medication or reduce the dose. Show me you can go out and do volunteer work or join a club. Prove to me that this is valuable to you, because I cannot continue to authorize access to a substance if you cannot show me that it’s actually helping you improve your quality of life.’ That’s the gauntlet I throw down to patients," Dr. Mark A. Ware said at the fifth Cooperative Meeting sponsored by the Consortium of Multiple Sclerosis Centers and the Americas Committee for Treatment and Research in Multiple Sclerosis.
Dr. Mark A. Ware
Through this requirement, a physician can validate that a patient with chronic non-cancer pain, epilepsy, HIV, multiple sclerosis, or any of the various other conditions for which medical marijuana is often used is not merely using the prescription recreationally, sitting around the house in a fog watching "M*A*S*H" reruns on television all day, explained Dr. Ware, a family physician and anesthesiologist who is director of clinical research at the Alan Edwards Pain Management Unit at McGill University in Montreal.
Canada has had a federal program for medical marijuana in place for a dozen years. Dr. Ware has extensive experience in prescribing medical marijuana in the pain clinic, where many patients report improvement not only in pain, but in spasticity, sleep, and/or mood. In addition, he has led randomized clinical trials that demonstrated that smoked cannabis reduced pain intensity and improved sleep quality in patients with chronic neuropathic pain (CMAJ 2010;182:E694-701) and that oral nabilone (Cesamet), a synthetic cannabinoid, improved sleep and was well tolerated in patients with fibromyalgia (Anesth. Analg. 2010;110:604-10).
He offered these tips for physicians who have patients asking about medical marijuana:
The doses used are modest: A World Health Organization report estimated that the average joint contains 0.5 g of cannabis, and that the average dose in patients using marijuana medically is four joints per day, or roughly 2 g of cannabis. That equates to 20-50 mg/day of tetrahydrocannabinol, the active molecule, which is consistent with the results of clinical trials using standardized extracts.
"A watchful dose is 5 g of cannabis per day. I would be very, very cautious about anybody who’s asking for more than 5 g/day. The likelihood of diversion goes way up. There’s very little reason on pharmacologic grounds why a patient would need that much," Dr. Ware advised.
Not everyone responds to medical marijuana: As with any other medication, there are nonresponders. Because cannabis has been widely available recreationally for so long, an individual’s past recreational experience can be used as a rough predictor of the likelihood of response to medical marijuana.
"One of the tests I use when a patient with a chronic medical illness comes in asking if maybe a cannabis-based drug could be useful is I ask if they’ve ever used the drug before, say, in college or high school. If they say they did and got anxious and paranoid and hated it, that tells me they’re not cannabinoid responders. I have no scientific evidence for this, it’s just a clinical tool I use. Prior positive recreational responders, I suspect, are more likely to have a favorable effect," Dr. Ware continued.
Most patients are more concerned about medical marijuana’s safety than effectiveness: Medical cannabinoids are "overall quite safe," according to the family physician, who with coauthors has published a systemic review of the adverse effects (CMAJ 2008;178:1669-78). Cannabis has no associated toxicity even at extremely high doses. The prescription oral cannabinoids have no apparent abuse potential. While dependence is seen in some recreational marijuana smokers, it doesn’t seem to occur with clinical use.
And regarding the key safety concern for most patients and physicians – the question of smoked marijuana’s effects on the lung (see accompanying story) – a new analysis of the published literature by one of the world’s pre-eminent pulmonologists, Dr. Donald P. Tashkin, emeritus professor of medicine and medical director of the pulmonary function laboratory of the University of California, Los Angeles, concluded that "the accumulated weight of evidence" suggests regular smoking of marijuana alone doesn’t increase the risk of lung or upper airway cancer or [chronic obstructive pulmonary disease] , and the evidence is inconclusive regarding a possible associated risk of lower respiratory tract infection (Ann. Am. Thorac. Soc. 2013;10:239-47).