LAS VEGAS – Planned clinical trials may clarify whether they benefit patients, said , professor of rheumatology at Rush University in Chicago.
Cannabinoid therapy “is on everybody’s mind, including our patients,” Dr. Block said at the annual Perspectives in Rheumatic Diseases held by Global Academy for Medical Education. “Cannabinoid receptors are widely present in all joint tissues, and endocannabinoids are clearly present in OA joint tissue. There is good evidence that the receptors regulate pain responses and central sensitization in a variety of OA animal models.” Where cannabis is legal, many people use it for chronic noncancer pain. Side effects may include altered perception, dizziness, drowsiness, and gastrointestinal adverse events.
Cannabis in the literature
“Nonetheless, if you do a systematic review of all of the randomized clinical trials of cannabinoids in human rheumatic diseases, what you will find is there is a grand total of four,” he said. The trials included patients with rheumatoid arthritis, OA, and fibromyalgia. An analysis of aggregated data found that cannabinoids improved pain and sleep, but all of the trials had a high risk of bias, poor allocation concealment, and poor blinding, said Dr. Block (Arthritis Care Res [Hoboken]. 2016 May;68:681-8.). “In OA, there is one randomized trial, and it was entirely null,” he said. “There was no positive effect on pain or on function in human OA” (Pain. 2012 Sep;153:1837-46.).
ClinicalTrials.gov lists two planned randomized controlled trials of cannabinoids – one using vaporized cannabis in patients with knee OA, and one using cannabidiol for hand OA and psoriatic arthritis. “Clinical trials are still scarce as of right now, so it will take a while before we have evidence for or against,” said Dr. Block.
Stem cell injections
Intra-articular stem cell injections are widely offered in the United States and abroad, he said. “In every newspaper, wherever I go, I open it up and there are full-page ads on stem cell injections that will cure everything that you want,” he said.
A systematic review of the effect of stem cell injections on structural outcomes and pain-related behaviors in animals found that “for all outcomes, the evidence quality was either low or very low,” Dr. Block said (Osteoarthritis Cartilage. 2018 Apr;26:445-61.). “Even in the animal models, it has been very hard to demonstrate any effect at all from just injecting stem cells into the joint.”
Systematic reviews of the evidence in humans have found that the data do not support the use of stem cell injections. The authors of one review concluded, “In the absence of high-level evidence, we do not recommend stem cell therapy” for knee OA (Br J Sports Med. 2017 Aug;51:1125-33.).
For another recent review, researchers screened hundreds of articles and identified 5 trials that met their inclusion criteria. They concluded, “Current evidence does not support the use of intra-articular [mesenchymal stem cells] for improving cartilage repair in knee osteoarthritis” (Arch Orthop Trauma Surg. 2019 Jul;139:971-80.).
Many clinical trials are planned, however. “Over the next several years, I would expect that we are going to get some real data on whether these are helpful or not,” Dr. Block said.
Meanwhile, some patients spend thousands of dollars to receive stem cell injections, and clinics report average patient satisfaction rates of 82%. “How can they be getting so much relief when there is no evidence that it is helpful? In fact, whatever evidence we have says that it is no better than placebo,” said Dr. Block. “Placebo itself is very potent....People always do what they feel helps them regardless of objective data, because placebo itself is very palliative.”
Dr. Block is a consultant for GlaxoSmithKline, Medivir, and Zynerba Pharmaceuticals. He has received royalties from Agios, Daiichi Sankyo, and Omeros. In addition, he has received grant or research support from AbbVie, Janssen, Novartis, Pfizer, and Kolon TissueGene.
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