Rheumatology Patients Should Avoid Herbal Cannabis Therapy

A group of researchers suggest that physicians discourage rheumatology patients from using medical marijuana as therapy for arthritis pain management.

In analyzing existing research, a team of investigators led by researchers from the McGill University Health Centre in Quebec, Canada aimed to provide healthcare professionals with medical evidence related to medical marijuana use in patients with rheumatic conditions, and to help physicians caring for patients that are self-medicating with marijuana to understand the health implications of using the drug.

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The researchers note that medical cannabis is commonly used to self-treat severe pain associated with arthritis and musculoskeletal pain, citing a previous study that found 80 percent of marijuana users in a United States pain clinic treat myofascial pain with the drug. Investigators also noted U.K. and Australian population studies that indicate up to 33 percent of individuals report using marijuana to treat arthritis pain.

The researchers point out, however, that concentrations of tetrahydrocannabinol (THC) vary in the plant material by up to 33 percent, and absorption rates are between 2 percent and 56 percent, which makes the dosing of herbal cannabis unreliable. Smoking marijuana, they add, is not recommended by the medical community, due to adverse effects on the respiratory system from hydrocarbons, tar, and carbon monoxide.

Furthermore, studies that show good efficacy of cannabinoids for cancer and neuropathic pain may not be extended to rheumatic diseases, because of the differing mechanism in the types of pain, according to the researchers. The authors highlight that use of medical marijuana comes with inherent risks such as compromised cognitive and psychomotor function, and long-term use of cannabis may lead to mental illness, dependence, addiction, and memory issues.

Given the lack of efficacy data, potential harm associated with the drug, and availability of other therapies, the authors find no support for the use of herbal cannabis as therapy for rheumatology patients, says Mary-Ann Fitzcharles, MD, researcher and rheumatologist at the McGill University Health Centre (MUHC) and the Research Institute of the MUHC in Quebec, Canada, and the study’s lead investigator.

“In the 21st century, physicians are expected to practice evidence-based medicine. When one looks at the evidence either for or against use of herbal cannabis to treat rheumatic complaints, it is clear that there is no sound evidence justifying use in rheumatology practice,” says Fitzcharles.

She adds, however, that “this is not to say there is no therapeutic potential for cannabinoid molecules. In fact, one of the messages from this review is that further research, particularly in rheumatology, is greatly needed.”

In jurisdictions where an exemption may be provided to allow for medical use of cannabis, physicians who are now expected to play a gatekeeper role should use their medical judgment and truly appreciate whether a recommendation for cannabis use in a particular patient is justified, adds Fitzcharles.

“In view of the large arsenal of studied pharmaceutical agents which may treat pain, physicians treating rheumatology patients have many options available to them before entering the relatively unknown world of medical cannabis. Until regulatory bodies have funded high quality research on herbal cannabis in rheumatic conditions, use of this treatment should remain exceptional.”

—Mark McGraw

Reference

Fitzcharles M, Clauw D, et al. The Dilemma of Medical Marijuana Use by Rheumatology Patients. Arthritis Care and Research. 2014.