There is not enough evidence to support using gels and creams containing rubefacients for chronic and acute pain, according to a systematic review by Cochrane Researchers. Rubefacients cause irritation and reddening of the skin, due to increased blood flow. The review focused on formulations containing salicylates, which are widely prescribed or sold over the counter as topical treatments for sports injuries and muscle pain.
"At present, due to a lack of high quality evidence, we can't say exactly how effective rubefacients are for acute injuries and there are certainly other more effective treatments which could be prescribed for use in chronic conditions like osteoarthritis," says lead researcher Andrew Moore, of the Nuffield Department of Anaesthetics at the University of Oxford in the UK.
There are over a million prescriptions each year for rubefacient gels and creams such as Movelat. As with Movelat, the rubefacient compounds in many of these products are salicylates, which, while they are related to aspirin, may not work in the same way, especially when applied to the skin. They are referred to as "counter-irritants" because it is thought that they offset localised pain through local skin irritation.
The review analysed data from 16 trials for acute and chronic pain, which together included 1,276 people. Only salicylates were studied and trials were generally small. Results from four studies showed topical salicylates performed better than placebos against acute pain, but excluding lower quality studies meant the results were not statistically significant. When used for chronic conditions, salicylates performed better than placebos. However, only one in six patients with chronic pain benefited substantially from using the muscle rubs compared to one in three using non-steroidal anti-inflammatory drugs.
"Larger and higher quality controlled trials of topical rubefacients are needed to establish whether these treatments really work. We also need more studies on other rubefacients as we were only able to assess the effectiveness of the salicylate formulations in this review," says Moore. "But it is important to remember that not all analgesic gels or creams are the same, and for others there is very good evidence of effectiveness. Those will be dealt with in other reviews presently being finalised."
Full citation: Matthews P, Derry S, Moore RA, McQuay HJ. Topical rubefacients for acute and chronic pain in adults. Cochrane Database of Systematic Reviews 2009, Issue 3. Art. No.: CD007403. DOI: 10.1002/14651858.CD007403.pub2.