Marijuana For Arthritis: What The Skeptics Say

Nearly two-thirds of Canadians prescribed medical marijuana use it to manage arthritis. Yet its potential as a treatment is still debated.
Oct 22, 2015

Published March 3 in Arthritis Care & Research, researchers from McGill University reviewed the body of evidence on marijuana for arthritis and concluded that there isn’t enough data to support its use.

“There is currently no good study of the use of medical marijuana for the use of rheumatic diseases,” says study co-author Dr. Mary-Ann Fitzcharles. “Which means that we have no studies that will speak to the good or the negative, the efficacy or side effects either in the short or the long term.”

Despite experiments in animals that suggest marijuana may reduce pain in arthritis, Dr. Fitzcharles and her team could only find a single study involving human patients.

“We have no studies that will speak to the good or negative”Published in 2005, the five-month trial followed 58 patients with rheumatoid arthritis and found treatment with Sativex, a pharmaceutical cannabis extract, provided significant improvements in pain, disease scores and sleep quality.

However, Dr. Fitzcharles’ paper asserts that the conclusions are “questionable,” due to flaws in the study’s design and the differences between Sativex and herbal cannabis.

Indeed, Sativex, an oral spray developed by GW Pharmaceuticals, holds a number of advantages over more basic cannabis preparations.

Yet at the molecular level, Sativex and cannabis aren’t much different at all. They both contain active ingredients called cannabinoids, which travel to different parts of the body via the blood stream.

‘Great Promise’

A team at Dalhousie University, led by Dr. Jason McDougall of the Department of Pharmacology, was the first to explain how cannabis might reduce arthritis pain. In 2007, his team confirmed specific pathways, called cannabinoid receptors, are present in human joints. They also showed that by activating these receptors, cannabinoids could reduce pain levels.

“Then we went on to see, okay, it can reduce the pain, can it actually reduce the inflammation? And we did some experiments where, yes indeed, the cannabinoids can reduce the inflammation of arthritis,” he recounts.

However, Dr. McDougall’s studies involved local injections of cannabinoids, which is different from how most patients administer the treatment.

“Anecdotal evidence comes from the arthritis pain population”“The benefit is you’re getting localized pain relief at the site where the pain is occurring and the drugs don’t get into the brain, so you don’t get the psychoactive side effects associated with a lot of cannabis derivatives,” he says.

Some of the osteoarthritis treatments like those tested in Dr. McDougall’s lab have made it to clinical trials. But the results weren’t as positive as expected, he says. He also acknowledges that there are many who use basic forms of cannabis and seem to find it helps.

“The anecdotal evidence comes from the arthritis pain population, who seem to gain some level of benefit from medical cannabis use for pain relief and helping with other symptoms like poor sleep patterns, etc.”

No group has added to the findings of the Sativex trial in the nine years since. Dr. McDougall says it’s unfortunate, because the results “showed great promise.”

Side Effects ‘Concern’

“I believe we have to find more selective cannabinoid drugs to use in clinical trials – that’s been the stumbling block,” explains Dr. McDougall.

Indeed, a greater barrier than the lack of clinical trials may be the fear of medical marijuana’s potential side effects.

“Our great concern is the impact on function of person using herbal cannabis. There are clearly effects on cognitive function and psychomotive control which are of great concern,” warns Dr. Fitzcharles.

On the other hand, current treatments for arthritis pain have their own drawbacks.

Long-term use of NSAIDs, Dr. McDougall says, is known to cause stomach and intestinal bleeding and kidney damage. Opioids, which are another type of painkiller commonly taken in arthritis pain, also come with a fair share of risks.

“All drugs have some level of side effects associated with them,” he explains, “and that’s no different from the current therapies that we’re using to treat arthritis pain.”

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