The National Center for Complementary and Integrative Health, a division of the National Institutes of Medicine, estimates that 38% of American adults use complementary and alternative medicine (including 17.7% who say they use “natural products”).1 Despite the popularity of these products, many providers remain skeptical—and for good reason. Enthusiasts may offer dramatic anecdotes to “prove” their supplements’ worth, but little scientific support is available for most herbal remedies. There are, however, exceptions—capsaicin, butterbur, green tea, and peppermint—as this review of the medical literature reveals.
Worth noting as you consider this—or any—review of herbals is that while there is limited scientific evidence to establish the safety and efficacy of most herbal products, they are nonetheless freely sold without FDA approval because, under current regulations, they are considered dietary supplements. That legal designation means companies can manufacture, sell, and market herbs without first demonstrating safety and efficacy, as is required for pharmaceutical drugs. Because herbal medications do not require the same testing through the large randomized controlled trials (RCTs) required for pharmaceuticals, evidence is often based on smaller RCTs and other studies of lower overall quality. Despite these limitations, we believe it’s worth keeping an open mind about the value of evidence-based herbal and botanical treatments.
Capsaicin, an active compound in chili peppers, provokes a burning sensation but also has a long history of use in pain treatment.2 Qutenza, an FDA-approved, chemically synthesized 8% capsaicin patch, is identical to the naturally occurring molecule.2 Topical capsaicin exerts its therapeutic effect by rapidly depleting substance P, thus reducing the transmission of pain from C fibers to higher neurologic centers in the area of administration.3
Meta-analyses and systematic reviews have shown capsaicin is effective for various painful conditions, including peripheral diabetic neuropathy, osteoarthritis (OA), low back pain (LBP), and postherpetic neuralgia (PHN).
Peripheral neuropathy. A Cochrane review of six randomized, double-blind, placebo-controlled studies of at least six weeks’ duration using topical 8% capsaicin to treat PHN and HIV-associated neuropathy concluded that high-concentration topical capsaicin provided more relief in patients with high pain levels than control patients who received a subtherapeutic (0.04%) capsaicin cream. Number-needed-to-treat values were between 8 and 12. Local adverse events were common, but not consistently reported enough to calculate a number needed to harm.4
OA. In randomized trials, capsaicin provided mild-to-moderate efficacy for patients with hand and knee OA, when compared with placebo.5-7 A systematic review of capsaicin for all osteoarthritic conditions noted that there was consistent evidence that capsaicin gel was effective for OA.8 However, a 2013 Cochrane review of only knee OA noted that capsicum extract did not provide significant clinical improvement for pain or function and resulted in a significant number of adverse events.9
LBP. Based on a 2014 Cochrane review of three trials (755 subjects) of moderate quality, capsicum frutescens cream or plaster appeared more efficacious than placebo in people with chronic LBP.10 Based on current (low-quality) evidence in one trial, however, it’s not clear whether topical capsicum cream is more beneficial for acute LBP than placebo.10
PHN. Topical capsaicin is an FDA-approved treatment for PHN. A review and cost-effectiveness analysis demonstrated that 8% capsaicin had significantly higher effectiveness rates than the oral agents (tricyclic antidepressants, duloxetine, gabapentin, pregabalin) used to treat PHN.11 The cost of the capsaicin patch was similar to a topical lidocaine patch and oral products for PHN.11 A meta-analysis of seven RCTs indicated that 8% topical capsaicin was superior to the low-dose capsaicin patch for relieving pain associated with PHN.12
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