Newswise — Popular over-the-counter creams, heat gels and other rub-on or spray-on remedies for sports injuries and arthritis aches are unproven and a waste of money, said the author of a new systematic review.
"The point is, you go to any pharmacy in the U.S. and find tons of these things, but they don't work," said Andrew Moore, a biochemist at the University of Oxford and senior author of the Cochrane review of 16 studies.
These preparations are thought to work by producing a counter-irritant effect. The warmth and redness they cause — and with some, the strong smell — distract users from, or offset, their musculoskeletal pain. Known as topical rubefacients, they can include a variety of active ingredients.
The review focused on preparations containing one or more salicylates. (Aspirin is a salicylate.)
"Some add local anesthetics, capsaicin, adrenal extracts. By and large it's a very mixed bunch," Moore said.
Familiar brands like Aspercreme contain a salicylate, as do Ben Gay and Icy Hot balms, which also have menthol additives. (Ben Gay and Icy Hot patches contain menthol alone.) Some, but not all reviewed preparations offer "heat action."
The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.
The topical medicine studies looked at participants ages16 and older. Seven studies included 697 people with acute conditions like strains or knee and ankle sprains and lower back injuries. Nine studies looked at 579 participants with chronic conditions like osteoarthritis, bursitis, older sports injuries and rheumatic back pain.
Most studies compared salicylate preparations with a placebo (sham) preparation lacking an active ingredient.
In acute pain studies, although 64 percent for patients in rubefacients group reported that their pain was reduced by half or more — compared with 34 percent for patients in the placebo group — this advantage was wiped out when researchers eliminated lower quality studies from the analysis.
The evidence for chronic conditions held up better, with pain relief success at two weeks of treatment reaching 45 percent for rubefacients group and 28 percent for placebo group.
One small study found that these preparations were no better than oral aspirin. In another small study of chronic pain, salicylates outperformed a preparation contained etofenamate, which is in the NSAID drug class that includes ibuprofen.
Data quality and quantity was a problem for the reviewers.
"We're looking at a few hundred patients. It's sobering," Moore said. "The smaller, older studies tend to show an effect while the larger, better, recent trials show no effect at all."
So what does help? Moore points to creams that the review did not cover:
"Topical local anesthetics work. Topical capsaicin works, particularly for some people with neuropathic pain. Some topical NSAIDs work extremely well in strains and sprains.
Capsaicin is a hot-pepper derivative. It was not used as a main ingredient in review studies but was sometimes present as an additive.
"With NSAID creams, you get good local concentration in the joints, unlike oral NSAIDS, where you only get a fraction of the medicine in the joints," Moore said.
But there's no sign that people will stop rubbing salicylates like Tiger Balm into a sore pitching shoulder or an arthritic knee.
Scott Zashin, M.D., is a clinical associate professor of medicine at the University of Texas, Southwestern Medical School and author of a book on arthritis pain. He recalls, "I used to use Ben Gay all the time when I played soccer. I felt better with it at that time." He said the warmth produced at the pain site might cause the muscles to relax.
He said topical rubefacients lead to "not much harm and even some safety advantages, for instance to people with problems taking oral meds." In osteoarthritis, taking oral "ibuprofen is more effective but it has potential side effects: drug interactions with aspirin, and GI complications for some people."
The review found few side effects from topical rubefacients when used correctly: applied in small amounts, only to the affected area. In the studies, people used the treatments at least once a day.
The UK and U.S. experts advise consumers to look at heat rubs and the like with a cold and wary eye.
"You have to look at cost," Zashin said. "A very expensive brand might not be more effective than a generic, but just have better marketing. It's not a miracle product."
The Cochrane review discloses that two co-authors have consulted for pharmaceutical companies and received lecture fees from them related to analgesics.
For his part, Moore calls on rubefacient makers to show more transparency: "If any of these products want to be taken seriously, they would make their chemical trials public and have them reviewed so that everyone could look at the evidence."
Would he recommend salicylate creams to consumers?
"I wouldn't waste the money. You might as well rub your skin with a bit of spit."
The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.
Matthews P, et al. Topical rubefacients for acute and chronic pain in adults. Cochrane Database of Systematic Reviews. Issue 3, 2009.