While marijuana may be widely used, either legally or otherwise, for the relief of arthritis pain and inflammation, there isn’t enough research to indicate when or if its use is warranted.

Members of the Arthritis Patient Advisory Board of Arthritis Research Canada receive invitations to attend the UBC Rheumatology rounds. We attended a session in April about the use of marijuana for the treatment of pain in people with rheumatic diseases. Perhaps the April date was no accident, as any Vancouver resident would recognize, although the event was held on the 4/17, not 4/20, when thousands of Vancouverites congregate downtown to smoke marijuana in what once was a demonstration of defiance, but now seems to be more of farmer’s market.

Dr. Mary-Ann Fitzcharles, a rheumatologist and pain researcher from McGill University, presented background information about herbal marijuana and the scarcity of evidence for its use in rheumatology. Dr. Fitzcharles is considered one of the foremost experts on the use of cannabis in arthritis and fibromyalgia. She began her talk saying that we don’t boil willow bark, a source of aspirin, to treat our headaches, nor do we use foxglove plants, a source of digitalis, to manage cardiac symptoms. She reminded us that tobacco was initially promoted as a medical treatment.

Here are the key points from the presentation:

• There is not a single well-controlled research study that has looked at the use of herbal cannabis in patients with rheumatic diseases, though there is some research in neuropathic pain.
• Cannabis has properties that affect pain, inflammation and have effects on the immune system that are still unknown.

Dosage issues

• Marijuana comes in vastly different potencies- the levels of tetrahydrocannabinol (THC) in any given plant can vary from 1-30%
• The amount of the THC molecule that reaches the blood (bioavailablility) can vary from 2-50%
• Illegal cannabis used for recreational purposes is today much stronger than that from previous decades
• Given these variables, it isn’t really possible to prescribe a given dose of herbal cannabis.
• The number of inhalations and length of breath holding add more variability to the drug blood level
• A joint is 0.5-1 gm of dried substance, rolled into a cigarette
• Cannabis contains hundreds of compounds, about 60 of them with cannabinoid properties. Some of these properties can influence the immune system, inflammation and pain

Known harms

• Mental development problems in young users. THC can recalibrate the sensitivity of the reward system and increases risks for addiction
• Psychomotor effects – coordination and attention problems
• Psychological problems – depression, suicide and risks for addiction
• Decreased cognitive function immediately after use that persists even when blood THC levels are very low
• Regular users have decreased cognitive function which may last for days (it sits in fatty tissue – like brains – for days)
• Doubles the rate of fatal car accidents
• 40% of Canadians aged 15-24 drove in the past 12 months within two hours of using cannabis
• 17% of fatally injured Canadian drivers had evidence of recent cannabis use
• People with arthritis are using herbal cannabis to treat their arthritis
• 44,000 Canadians report using it for musculoskeletal problems and 66% say they have severe arthritis
• Will your doctor give you a prescription for herbal cannabis?
• As of April 2014, MDs in Canada can sign a document that enables a patient to access herbal cannabis from a grower. As cannabis is not a Health Canada approved product, and without a conduit via a pharmacy, this document is not truly a prescription.
• MDs can document a recommendation to use up to five mg/day.
• No other drug is prescribed this way
• A doctor is expected to practice evidence-based medicine to meet their practice standards
• If an MD writes a prescription/documentation they are fully responsible
• Given medical practice standards and codes of ethics, Dr. Fitzcharles stated that recommending the use of herbal cannabis for patients with rheumatic disease is not practicing evidence-based medicine.

Thousands of Canadians with arthritis are using cannabis to treat their arthritis. Perhaps some of those people (self-reported) use it as a means to legally access the drug for recreational purposes. The majority of the people at the Rheumatology Rounds believed herbal cannabis should be legalized. Given its purported pain relieving and immune system effects, patients need to lobby for more research into the benefits and harms of the active ingredients of herbal cannabis. There needs to be a way to standardize and evaluate doses of the active ingredients for different disease groups and ages.

Don’t expect your MD to write a recommendation for herbal cannabis in your chart. With the lack of research evidence, dosage control and all the potential dangers, it is likely that some medical practitioner will eventually be taken to court. Don’t let it be your rheumatologist.