EFFICACY OF TOPICAL ANALGESICS AS AN INTERVENTION FOR ACUTE AND CHRONIC PAIN. Jodi G. Handler; Kirsten L. Bonn*; Cynthia L. Riley; Katherine R. Savillo; George E. Xenakis MPT Program, University of Medicine and Dentistry of NJ and Rutgers University Graduate School at Camden, Stratford, NJ UNIQUE: Acute and chronic pain sufferers continuously seek relief through topically applied over-the-counter (OTC) products. OTC topical analgesic products have become a billion dollar industry that is growing as a result of the population′s demand for alternative means of controlling pain. Manufacturers of OTC topical analgesic products claim that their products provide relief from acute and chronic pain. In support of evidence based practice, clinicians are searching for the efficacy and safety of topically applied OTC analgesic products as the Food and Drug Administration approvals are still pending. Physical therapists are in a position to assist and guide their patients/clients, in identifying topical analgesic products whose claims are supported by evidence. Clinical practice can be enhanced by a critical review of the literature for the safe and effective application of OTC topical analgesic products. PURPOSE: The purposes of this project were to identify OTC topical agents that are effective in reducing acute and chronic pain with minimal side effects and apply the results to physical therapy practice. FOUNDATION: Topical analgesics are typically applied to the skin with the intention of providing pain relief by invoking the gate control theory to block the painful stimulus. It is commonly believed that the gate can be closed by stimulating larger diameter nerve fibers (A-alpha and A-beta) which will inhibit the transmission of the smaller nerve fibers (A-delta and C) carrying the painful sensations. Topically applied analgesics are thought to stimulate the A-alpha and A-beta fibers to relay the pain blocking message to the substantia gelatinosa faster than the A-delta and C nerve fibers. DESCRIPTION: A literature review was performed from January to June 2004. Capsaicin, menthol, methyl salicylate (MS), camphor, and trolamine salicylate (TS) were the five most common active ingredients identified from brand name products. Databases (OVID, Medline, CINAHL, OVID Full Text, Dissertation abstracts, and PubMed), trade magazines, and internet web sites were searched. Studies were included if the topical agent being examined was used for pain relief and was within the physical therapy scope, written in English, and published after 1960. Products had to be topically applied and the subjects had to be human. Studies were excluded if the topical analgesic was only available with a prescription and used with other modalities. OBSERVATIONS: There is a lack of available research documenting the mechanism of action and the efficacy of camphor, menthol, MS, and TS. The research reviewed failed to support the effectiveness of these agents for localized pain relief, with the exception of one case study that provided support for the use of menthol for postherpetic neuralgia. The mechanism of action and efficacy of topically applied capsaicin is better documented. Twenty-three studies investigated the effectiveness of capsaicin for specific pathologies including diabetic neuropathy (DN), polyneuropathies (PN), osteoarthritis (OA), rheumatoid arthritis (RA), post-mastectomy pain syndrome (PMPS), reflex sympathetic dystrophy syndrome (RSDS), chronic neck pain (CNP), cancer (CA), and temporal mandibular joint (TMJ) pain. Based on the evidence reviewed, the pain relief provided from capsaicin appeared pathology dependent. Additionally, these studies consistently suggested that the amount used during daily application and length of treatment appeared to positively impact the degree of pain relief provided. Burning was the most common side effect reported, ranging from mild to severe. However, these studies repeatedly documented that the burning intensity and incidence decreased over time. Many of the specific pathologies investigated are chronic diseases however; none of the studies looked at the use of capsaicin as a life long solution. Many participants identified in the studies were active community dwellers over the age of 55 years old that would commonly access private practice physical therapy services for pain relief. CONCLUSIONS: The results of this literature review revealed that there is limited research available related to the effectiveness of topical analgesics containing menthol, camphor, MS, or TS. Numerous studies indicated that capsaicin is effective for pain relief in individuals with DN. However, studies supporting capsaicin for decreasing pain for individuals with OA, RA, and PMPS were limited. Single studies provide minimal evidence for the use of capsaicin for pain relief in CNP, CA, RSDS. Finally, the single studies of capsaicin use for PN and TMJ pain provided no support. Based on the findings there is a hierarchy of evidence that supports the efficacy of capsaicin for various chronic and acute pathologies. Accordingly, additional research should focus on the efficacy, safety, and parameters of application by specific pathology. According to the Code of Ethics the tenets of ethical physical therapy promote responsible, competent, and safe practices in which ″the physical therapist shall provide and make available accurate and relevant information to patients/clients about their care″ (APTA, 2001, p.689). Therefore, it is an essential part of physical therapy practice to educate patients/clients on the use of these products as well as their potential side effects, such as burning with capsaicin. REFERENCE: American Physical Therapy Association. (2001). Guide to Physical Therapist Practice (2nd ed.). Alexandria, VA: APTA. FUNDING SOURCE: None KEYWORDS: Pain, Topical analgesics, Pain relief, Capsaicin, Topical agents Copyright 2009 by the American Physical Therapy Association. Requests for reprints should be directed to the corresponding author of the article. Educators, students, and other academic customers may receive permission to reprint copyrighted material from Physical Therapy (ISSN 1538-6724) by contacting the Copyright Clearance Center Inc, 222 Rosewood Dr, Danvers, MA 01923. Other types of customers who want permission to reprint should contact the APTA Editorial Office, Attn: Physical Therapy.