Try Capsaicin Cream for Painful Conditions

Summarized by Robert W. Griffith, MD
April 15, 2005

Introduction

Capsaicin comes from chilli peppers, so it's not surprising that it's hot. But once the heat has subsided, it can bind closely to pain receptors in the skin (and beneath the skin), reducing their sensitivity to painful stimuli. With the recent withdrawal of Vioxx and Bextra, and the doubt cast on the safety of high-dose NSAIDs, patients are looking at new ways to combat pain in muscles, joints, and nerves. Researchers at Oxford University, UK, have analyzed the published reports of the safety and effectiveness of capsaicin in a cream for topical application. Their findings, published in the British Medical Journal, are summarized here.

What was done

Topical capsaicin has been used to treat pain originating in nerves (postherpetic neuralgia in shingles, diabetic neuropathy), muscles and joints (osteoarthritis, rheumatoid arthritis). The investigators searched databases for randomized controlled clinical trials published in recognized medical journals.¹

They found a number of trials that fulfilled their requirements - treatment had to be applied 3-4 times daily, and there had to be at least 10 patients in each treatment group. The results closest to 4 weeks of treatment for arthritis and to 8 weeks of treatment for neurological conditions (shingles, diabetic neuropathy) were selected for pooled analysis. The number of patients who achieved at least a 50% reduction in their pain was used as the primary measure of effectiveness.

Side effects were analyzed, as were the number of patients stopping treatment because of side effects.

The overall results

There were six trials (656 patients) suitable for analysis of effectiveness in nerve conditions. Overall, capsaicin 0.075% cream was 1.4 times as effective as placebo. Put another way, more than 5 patients would need to be treated to have one patient experience a 50% reduction in pain.

For arthritic pain, three studies provided data from 368 patients. Capsaicin (0.025% cream or applied on a plaster) was 1.5 times as effective as placebo; 8 patients would need to be treated to have one patient achieve a 50% improvement in pain.

About a third of the patients experienced localized side effects of capsaicin - itching, prickling, or burning. One in ten patients withdrew from treatment because of these side effects.

What these results mean

For centuries, herbalists have recommended rubbing red pepper into sore muscles and joints. Obviously, they had a good basis for their recommendation - capsaicin. The substance is effective. But the analyses done suggest capsaicin is slightly less effective that previously thought.

It should be noted that the placebo response was 42% for nerve pain, and 25% for arthritis pain. (These rates are similar to those found for placebo tablets in oral analgesic drug studies.) The large placebo response rate sets a high hurdle for a new treatment to jump, and capsaicin did as well as most oral analgesics in such studies.

However, the side effects are not inconsiderable. And three or four times daily applications of a cream is not exactly user-friendly. We suggest that patients try the cream themselves for a few weeks, to see if the benefits outweigh the disadvantages. There are, after all, other non-drug approaches to pain management (see the links below).

Source

• Systematic review of topical capsaicin for the treatment of chronic pain. L. Mason, RA. Moore, S. Derry, JE. Edwards,  et al., BMJ, 2004, vol. 328, pp. 991--994

Footnotes
1. By a 'randomized, controlled' trial we mean a trial in which the patients are allocated at random to receive the active treatment being studied or a control treatment - this may be a placebo (dummy treatment) or a known active treatment.

Related Links
Shingles, When You're Older
Acupuncture for Knee Arthritis?
Knee Osteoarthritis? Call in the Leeches!
NINDS: Peripheral Neuropathy

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