Evidence to support the use of topical capsaicin is limited in terms of quality and quantity. No systematic reviews were found on the use of topical capsaicin in people with osteoarthritis, but evidence from four small RCTs found that short-term use of topical capsaicin was beneficial compared with placebo. Evidence from an economic evaluation of the use of topical capsaicin was also favourable in support of its use.

• The National Institute for Health and Clinical Excellence (NICE) looked at studies that investigated the efficacy and safety of topical capsaicin compared with oral nonsteroidal anti-inflammatory drugs (NSAIDs) or placebo with respect to symptoms, function, and quality of life in adults with osteoarthritis.
• Four RCTs (n ranging from 59–200) were appraised on topical capsaicin versus placebo (given four times daily) and focused on symptoms, function, and quality of life in people with osteoarthritis. All trials were parallel group studies and were considered methodologically sound. However, the site of osteoarthritis differed, and study duration varied from 4–12 weeks.

Topical capsaicin compared with placebo

• In terms of:
• Pain relief — with different outcomes, topical capsaicin was generally significantly more effective than placebo (with a trend towards being more effective the longer the treatment was used).
• Reduction in morning stiffness — only one RCT reported on this and no significant difference was found between capsaicin and placebo.
• Function outcomes — topical capsaicin was significantly more effective than placebo in grip strength (as measured by the percentage change from baseline).
• Global assessment outcomes — topical capsaicin was significantly more effective than placebo.
• Quality of life outcomes — only one RCT reported on this and no significant difference was found between capsaicin and placebo.
• Adverse events:
• One RCT (n = 59) reported that, over 9 weeks, 20 people (69%) using topical capsaicin for osteoarthritis of the hand had adverse events while 9 people (30%) using placebo had adverse events.
• Four RCTs (n = 70, 59, 113, and 200) reported rates of withdrawals due to adverse effects — topical capsaicin compared with placebo: 3% vs. 14%; 14% vs. 23%; 20% vs. 11%; and 20% vs. 20%.

Economic evaluation

• NICE looked at studies that conducted economic evaluations involving topical capsaicin.
• An Australian study considered topical capsaicin compared with placebo and other drugs for people with osteoarthritis [Segal et al, 2004]. Data regarding the effectiveness of capsaicin was taken from the literature and the data were analysed in terms of the quality adjusted life year (QALY) gain.
• Topical capsaicin was found to be cost effective compared with placebo, since it brings QALY gains at relatively low cost. In comparison to other drugs, topical capsaicin appeared likely to be closer to the cost of coxib NSAIDs, and significantly more expensive than some standard NSAIDs in a UK setting. However, some estimates do not include the adverse event costs of these drugs and given this, it is difficult to make reliable recommendations based on the Australian data.
• There are limited data showing some positive effects from topical capsaicin, with short-term follow up. Although the evidence is limited to knee osteoarthritis, the NICE guideline development group were aware of widespread use in hand osteoarthritis as part of self-management, and felt that the data on efficacy at the knee could reasonably be extrapolated to the hand. No serious toxicity associated with capsaicin use has been reported in the peer-reviewed literature.

[National Collaborating Centre for Chronic Conditions, 2008]