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19 Articles in Volume 19, Issue #6
Arthrofibrosis: Targeting Hormones after Childbirth to Relieve Frozen Shoulder, Inflamed Joints
Can CGRP Help Clarify Why Migraine Is More Common in Women?
Case Report: Managing Chronic Pelvic Pain in Men
CGRP Monoclonal Antibodies for Chronic Migraine: Year 1 of Clinical Use
Chronic Pelvic Pain as a Form of Complex Regional Pain Syndrome
Correspondence: Continuing the “Pain Specialist” Dialogue
Endometriosis and its Misunderstood Etiology
Evolving Management Strategies for Osteoarthritic Pain
Gamma PEMF Therapy: A Pilot Study For Its Use in Managing Opioid Addiction
Guest Editorial: Sex Differences in Pain
How to Provide Effective Pain Management to LGBTQ Individuals
Interscalene Peripheral Nerve Stimulation for Post-Operative Chronic Shoulder Pain
New ICD-11 Codes Set to Improve Pain Care in the Primary Setting
Perspective: Could NGF Antagonists Be the Safest, Most Efficacious Class of Drug We Have to Treat Pain?
Rheumatoid Arthritis and Cognition: Is There a Genetic Link?
Targeting Nerves Provides Alternative to Opioids for Joint Arthroplasty
The Sex Question in Primary and Pain Care
What is capsaicin’s role in treating osteoarthritis?
When Pain Clinicians Have to Be the Villain: Communication Strategies to Bridge the Divide

What is capsaicin’s role in treating osteoarthritis?

September/October 2019 Ask the Expert: Inside the analgesic properties of the extract capsaicin for OA.
Pages 28-29

Osteoarthritis affects roughly 27 million Americans and is the most common joint disease in the United States.1 Pain from osteoarthritis (OA) may stem from activation of nociceptive nerve endings in the joint, microfracture, periosteal irritation, damage to ligaments, synovium, or the meniscus, and synovial capsule distension due to increased joint fluid.2

The most recent guidelines from the American College of Rheumatology (ACR) provide recommendations for the treatment of hand, knee, and hip osteoarthritis. The ranking of recommendations in these guidelines is classified as strong or conditional. A conditional recommendation lacks high-quality evidence and/or has evidence with only a small difference between desirable and undesirable effects. The ACR conditionally recommends topical capsaicin along with topical NSAIDs (including trolamine salicylate), oral NSAIDs (including COX-2 selective inhibitors), and tramadol for hand OA.3 The guidelines conditionally recommend that patients with knee OA use acetaminophen, oral NSAIDs, topical NSAIDs, tramadol, and intraarticular corticosteroid injections, while conditionally recommending against the use of topical capsaicin. Worth noting, the guidelines make no mention of topical capsaicin in their recommendations for the treatment of hip osteoarthritis.3

The analgesic properties of the extract is reviewed. (Source: 123RF)

How Capsaicin Works

Capsaicin activates nerve fibers in the skin. With repeated applications of topical capsaicin, the fibers become desensitized due to reversible nerve degeneration. This degeneration is accompanied by the depletion of substance P, which impairs pain transmission.1,4 Capsaicin acts by binding to Transient Receptor Potential Vanilloid-1 (TRPV1) receptors and then causing a decrease in membrane resistance, depolarization, and activation of synaptosomal neurotransmitter release. This desensitization and depletion of neurotransmitters produces an analgesic effect. With regular exposure, nerve terminals will degenerate, causing prolonged analgesic effects upon completion of treatment.5

Analgesic Data on Capsaicin

One Cochrane review evaluated herbal topicals for the treatment of osteoarthritis. The review was small, evaluating seven studies, with only one (n = 99) evaluating the use of a topical capsicum extract gel in the treatment of OA of the knee over four weeks.5 The study used a Visual Analog Scale (VAS) ranging from 0 to 100 to evaluate pain, with the treatment group rating pain 44.6 out of 100 compared to 45.6 out of 100 in the placebo group. The authors of this review concluded that, since the improvement of pain with capsicum extract gel was not statistically significant, and it had commonly associated side effects of burning and irritation, that it would probably not improve pain or function related to osteoarthritis of the knee.5

When discussing the efficacy of topical capsaicin, studies have found it to be most effective in treating pain caused by OA of the hand. One study found that capsaicin 0.075% cream applied four times a day significantly improved both pain and tenderness; however, there was no improvement in swelling, grip strength, duration of morning stiffness, categorical pain ratings, or function when analyzed using the Health Assessment Questionnaire.4 Although it may improve pain and swelling, capsaicin may not improve other aspects of the condition that patients may find concerning.

One of the largest barriers for patients when initiating topical capsaicin therapy are the adverse effects experienced. A review of 16 studies, which cumulatively enrolled 1,556 subjects, found that 54% of patients treated with topical capsaicin experienced adverse reactions, compared to 15% of patients in the placebo groups. The most common adverse reaction reported was a burning sensation. From these 16 studies, about 203, or 13%, of patients treated with capsaicin discontinued treatment due to the significant burning sensation it caused.4 Along with the usual side effect of burning, accidental contact with eyes while using capsaicin on the skin may also cause severe irritation and burning. For this reason, patients should wash their hands immediately after application.4 How patients should wash their hands, such as only washing the palms while leaving the cream on the tops, or not washing them at all depending on the area being treated (eg, if used for hand OA) is important and should be discussed with patients preparing to start topical capsaicin therapy.2

Alternative Topical Options

Due to the burning effects patients experience with topical capsaicin, many patients are likely to discontinue its use, particularly early in treatment. These patients may turn to other over-the-counter (OTC) treatments, such as lidocaine patches and other counterirritants (eg, menthol and camphor, two active ingredients commonly found in products like Icy Hot). While these products are considered safe, data of their effectiveness for osteoarthritis is lacking. Lidocaine patches work by impairing membrane permeability to sodium, thus blocking impulse propagation, dampening peripheral nociceptor sensitization and eventually central nervous system hyperexcitability.6 Counterirritants, or topical rubefacients, such as menthol, camphor, and topical salicylates, exert their pain-relieving effects by causing blood vessel dilation, which causes a soothing feeling.3 Along with the soothing feeling, the idea of irritating painful areas to alleviate pain comes from the thought that, when served by the same nerves, the irritation may alter or offset pain signals.3 Counterirritants, menthol in particular, have been studied for use in treating OA pain. While there has not yet been definitive evidence for the use of these products, some studies have shown menthol as having potentially beneficial effects in treating osteoarthritis.7 See Table I.

It is important to discuss with patients the options for OTC topicals for pain, especially in relation to osteoarthritis. While lidocaine patches and products such as Icy Hot may be attractive to patients due to their relatively low price and recognizable marketing, recommending products should be based on evidence to support use and patient-specific factors. Patients should be informed about efficacy and which products are intended to treat pain specifically resulting from OA. Although capsaicin cream may not be the most pleasant treatment due to side effects, it may be part of the conversation for managing pain associated with OA of the hands.

Last updated on: October 7, 2019
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