Chili peppers no longer belong only in the kitchen. A derivative of these members of the nightshade family, chili peppers are now being heralded as the newest form of pain reliever and a treatment for gastric hyperacidity. The responsible chemical is capsaicin, which is the component that provides the peppers their trademark spice and pungency. Chili peppers, scientifically classified as Capsicum frutescens and popularly referred to as cayenne pepper or hot pepper, are related to paprika, pimiento, and red or green bell peppers.1

Background

Capsaicin was first isolated and given its name in 1816. Chemists P.A. Bucholtz, L.T. Tresh, and later Endre Hogyes proved that capsaicin caused a burning sensation when placed in contact with mucous membranes. Capsaicin, an oleoresin, is believed to be synthesized in the thin, fibrous septa of chili peppers. The substance is present in large quantities in this tissue and increases in concentration as the fruit forms seeds connected to these internal membranes.1 While poorly soluble in water, capsaicin is readily dissolved in oily mixtures.2

The “heat” (pungency) from foods such as capsaicin is typically measured by high-performance liquid chromatography, but the more familiar measurement is known as the “Scoville unit.”3 In the test developed by Wilbur Scoville in 1912, a solution of the pepper extract is diluted in sugar water until the heat is no longer detectable by a panel of tasters; the degree of dilution gives its measure on the Scoville scale. Pure capsaicin has a Scoville heat unit rating of 15 million. For comparison, a bell pepper (containing no capsaicin at all) has a Scoville rating of zero, and a habanero pepper rates around 200,000. Because of its subjective nature, the Scoville test is imprecise.4


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Science

Capsaicin for the purpose of pain relief has been most commonly compounded into a topical cream or gel. At least 13 of 16 randomized controlled trials involving more than 1,500 participants found capsaicin cream to be more effective at pain relief than placebo. These studies looked at pain relief in arthritis sufferers, people with chronic back pain, and those with neuropathic pain (including post-herpetic as well as diabetic neuropathy). One study examined capsaicin’s antipruritic effect on patients with psoriasis and found it to be significantly better than placebo at relieving the chronic itching of this skin condition.1

Capsaicin’s mechanism of action for pain relief centers around the ability of the active molecule to enter the dermal layer deeply enough to encounter the tiny nociceptor nerve-fiber endings associated with the pain response and “hyperexcite” them, causing a massive release of inflammatory mediators (substance P and calcium). Because neuronal cells are not equipped with an endless supply of these substances, this assault depletes the cells’ stores, leaving them unable to further trigger a pain and inflammation response.5

When taken orally, foods and other preparations containing capsaicin provide the classic hot sensation as they come into contact with mucous membranes. Some data show an antibacterial effect against the ulcerogenic bacterium Helicobacter pylori with capsaicin. This use requires a delicate balance—too much capsaicin can induce erosive gastritis symptoms by lowering the gastric pH too far, but in situations of simple indigestion caused by overeating, etc., before-meal capsaicin acts as a gastroprotective agent and facilitates digestion and gastric mucosal blood flow.2

Use and how supplied

Since capsaicin is a food-source plant in and of itself, the range of available forms is quite broad. Many people prefer to incorporate capsaicin in their daily foods and cooking, thereby avoiding any need for artificial supplementation. When cooking with fresh peppers, it is advisable to wear rubber gloves to prevent the oily resin that bears the heat from coming into direct contact with the skin. Always remember to wash the hands thoroughly after working with the peppers and before touching any other part of the body (e.g., rubbing the eyes). If capsaicin gets into the eyes, flush with water. If capsaicin gets on other sensitive areas of the body, wash the areas with warm (not hot) soapy water.

OTC capsaicin creams and gels are available in concentrations ranging from .025% to .075%.2 Most topical capsaicin products suggest four applications daily. If you don’t wear gloves when applying the product to the body, be sure to wash your hands thoroughly afterward. Many patients are lulled into complacency and forget to clean their hands because the initial application of topical products does not always elicit an immediate burning sensation. These patients will learn their lesson quickly, however, if they touch their eyes or other mucosal surfaces.

Safety, drug interaction

The most common side effect of topical capsaicin products is a rash.2 When that happens, the product should be discontinued. If the strength can be reduced and the patient wishes to rechallenge, there is no contraindication. No drug interactions have been noted with topical use.

Tell patients choosing to treat indigestion problems with oral capsaicin to consult with you before beginning a regimen. Those patients with personal histories of duodenal or gastric ulcer should be especially cautious. Additionally, anyone on a blood-thinning agent should avoid oral capsaicin because of the increased risk of erosive gastric bleeding.2

Cost

Whether in fresh form or pharmaceutical-grade topical preparations, capsaicin is extremely inexpensive. A one-month supply of gel or cream should cost no more than $12-$15.

Summary

The GI risks (not to mention risks to renal and other organ systems) of traditional pain medications (e.g., nonsteroidal anti-inflammatory drugs) are well documented. Hepatic injury due to acetaminophen use is also common. For well-defined uncomplicated arthritic or neuropathic pain with intact dermis, topical capsaicin is an effective, safe, evidence-based alternative. Use for gastric protection and digestive facilitation should be discussed with a health-care provider to assure safety before use.

Ms. Sego is a staff clinician at the Veterans Administration Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.

References

1. About.com Capsaicin cream. Available at http://altmedicine.about .com/od/. Accessed March 6, 2008.

2. Skidmore RL. Mosby’s Handbook of Herbs & Natural Supplements. 3rd ed. St. Louis, Mo.: Elsevier Mosby; 2006:223.

3. Wikipedia. Capsaicin. Available at http://en.wikipedia.org/wiki. Accessed March 6, 2008.

4. Wikipedia. Scoville scale. Available at http://en.wikipedia.org/wiki/Scoville. Accessed March 6, 2008.

5. Caterina MJ, Schumacher MA, Tominaga M, et al. The capsaicin receptor: a heat-activated ion channel in the pain pathway. Nature. 1997;389:816-824.