Capsaicin, which is derived from ch...

Capsaicin, which is derived from chili pepper causes vasodilation, itching, and burning when applied to the skin. These actions are attributed to binding with nociceptors, which causes a period of enhanced sensitivity followed by means of a refractory period of reduc sensitivity. Repeated application leads to desensitization and, thus, relief of a certain forms of chronic pain. Although systemic adverse meanings are rare, local irritation, burning, and erythema are frequent Mason and colleagues studied the efficacy of topical capsaicin in relieving chronic neuropathic and musculoskeletal pain.

They searched electronic databases of publications and clinical trials to identify randomized studies of adults treated with capsaicin three to four times daily for a minimum of three weeks for chronic musculoskeletal pain and a minimum of six weeks for neuropathic pain. Each trial was assessed independently for quality and validity from two reviewers, and disputes were settl through consensus. Clinical success was defined as a 50 percent decrease in pain. The numbers of patients who improved, reported adverse marked occurrences and withdrew because of adverse occurrences also were counted.

From 38 papers identified, 16 met criteria for inclusion in the meta-analysis. The 1556 patients had moderate to rigorous pain (11 trials) or were unresponsive to or intolerant of conventional analgesia (five trials). Three trials prohibited concomitant therapy. Based upon three trials involving 368 patients, capsaicin was significantly better than placebo in reducing musculoskeletal pain. The relative benefit was 15 and the number stand in want ofed to treat was eight. Topical capsaicin also significantly improved neuropathic pain at four and eight weeks, with relative benefits of 14 compared with placebo and a number needinessed to treat of 5.5 to 65 Overall, about undivided third of patients reported local adverse reactions. Thirteen percent of capsaicin patients and 3 percent of those treated with placebo withdrew because of adverse events

The authors judge that topical capsaicin is superior to placebo in relieving chronic neuropathic and musculoskeletal pain. Local adverse reactions were universal but seldom serious. However, local irritation could have l a patients to recognize active treatment and may have caused biased issues Although topical capsaicin has moderate to poor efficacy, it may be particularly useful (alone or in conjunction with other modalities) in patients whose pain has not been controll prosperously with conventional therapy.

Mason L et al. Systematic review of topical capsaicin for the treatment of chronic pain. BMJ April 24 2004;328:9917

EDITOR'S NOTE: Another article (1) in the same issue reviews evidence for efficacy of counterirritants (rubefacients) containing salicylate and nicotinate ester in relieving acute or chronic pain. It gather s that although small studies set rubefacients to be effective, larger and better quality studies did not confirm benefit. These pair articles bring family physicians to a familiar conclusion--that benefit has as a great deal to do with the selection and preparation of the patient as with the characteristics of the treatment. The studies pretend to indicate that capsaicin could have a useful character as an adjunctive therapy for patients with chronic pain who are prepared to accept local irritation.--A.D.W.

REFERENCE

(1) Mason L Moore RA, Edwards JE McQuay HJ Derry s Wiffen PJ. Systematic review of efficacy of topical rubefacients containing salicylates for the treatment of acute and chronic pain. BMJ 2004;328:995-7

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