Topical capsaicin for chronic neuropathic pain in adults

[Guest guest]

Cochrane Database Syst Rev. 2009 Oct 7;(4):CD007393.

Topical capsaicin for chronic neuropathic pain in adults.

Derry S, Lloyd R, RA, McQuay HJ.

Pain Research and Nuffield Department of Anaesthetics, University of Oxford,

West Wing (Level 6), Radcliffe Hospital, Oxford, Oxfordshire, UK, OX3 9DU.

BACKGROUND: Topical creams with capsaicin are used to treat pain from a wide

range of chronic conditions including neuropathic pain. Following application to

the skin capsaicin causes enhanced sensitivity to noxious stimuli, followed by a

period with reduced sensitivity and, after repeated applications, persistent

desensitisation. There is uncertainty about the efficacy and tolerability of

capsaicin for treating painful chronic neuropathies.

OBJECTIVES: To review the evidence from controlled trials on the efficacy and

tolerability of topically applied capsaicin in chronic neuropathic pain in

adults.

SEARCH STRATEGY: Cochrane CENTRAL, MEDLINE, EMBASE and Oxford Pain Relief

Database, searched in May 2009.

SELECTION CRITERIA: Randomised, double blind, placebo controlled studies of at

least six weeks' duration, using topical capsaicin to treat neuropathic pain.

DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trial

quality and validity, and extracted data. Information was extracted on numbers

of participants with pain relief (clinical improvement) after at least six

weeks, and with local skin reactions, and used to calculate relative risk and

numbers needed to treat to benefit (NNT) and harm (NNH). Details of definition

of pain relief and specific adverse events were sought.

MAIN RESULTS: Six studies (389 participants in total) compared regular

application of low dose (0.075%) capsaicin cream with placebo cream; the NNT for

any pain relief over six to eight weeks was 6.6 (4.1 to 17). Two studies (709

participants in total) compared a single application of high dose (8%) capsaicin

patch with placebo patch; the NNT for >/= 30% pain relief over twelve weeks was

12 (6.4 to 70). Local skin reactions were more common with capsaicin, usually

tolerable, and attenuated with time; the NNH for repeated low dose application

was 2.5 (2.1 to 3.1). There were insufficient data to analyse either data set by

condition or outcome definition. All studies satisfied minimum criteria for

quality and validity, but maintenance of blinding remains a potential problem.

AUTHORS' CONCLUSIONS: Capsaicin, either as repeated application of a low dose

(0.075%) cream, or a single application of a high dose (8%) patch may provide a

degree of pain relief to some patients with painful neuropathic conditions.

Local skin irritation, which is often mild and transient but may lead to

withdrawal, is common. Systemic adverse effects are rare. Estimates of benefit

and harm are not robust due to limited amounts of data for different neuropathic

conditions and inconsistent outcome definition.

PMD: 19821411