Capsaicin Patch Eases Postherpetic Neuralgia Pain

April 03, 2003

April 3, 2003 (Honolulu) — A one-hour application of a capsaicin patch placed on an affected area of a patient suffering from postherpetic neuralgia appeared to reduce the pain by at least 33% for up to one month for many treated participants in a multicenter pilot study.

The pain decrease of 33% was reported by 42% of patients in a high-dose treatment group compared with an 8% pain reduction in a control group who were given a low concentration placebo patch of .04% that was largely ineffective, but provided users with the false sensation of receiving a treatment.

Forty-four patients were involved in the study at nine centers in the United States. Twenty-six were in the high-concentration capsaicin group, and the remainder were in the control group.

The patients had suffered from the chronic pain of the disease for an average of three years, but some have been dealing with the pain for up to 13 years, said Misha-Miraslav Backonja, MD, a neurologist at the University of Wisconsin in Madison. They had been taking antidepressant medication, tricyclic antidepressants, anti-epileptic medications, and opioid analgesics.

"They were taking medication, but that was not enough," Dr. Backonja told Medscape, which was why they sought further pain therapy and were entered into the trial.

In a presentation here as part of the late-breaking science program at the American Academy of Neurology 55th annual meeting, Dr. Backonja said patients were first treated for one hour by a local anesthetic, to prepare for the placement of the highly concentrated capsaicin patch. The patches were up to 1,000 cm2. They were placed on the most painful spot, but not on the face.

Low concentrations of capsaicin, the pungent ingredient in hot chili peppers, has been used for many years in creams with varying success for the treatment of postherpetic neuralgia and other peripheral neuropathies. Their use has been limited by pain and inconvenience caused by the requirement for multiple daily applications for weeks to attain efficacy.

Capsaicin activates vanilloid receptors expressed in dermal and epidermal nociceptive sensory nerve fibers. This leads to burning pain sensations followed by functional inactivation of those nociceptors.

Kenneth Nakano, MD, a neurologist from Waikiki, Hawaii, who co-chaired the session with Dr. Backonja, told Medscape that "there may be some basis for [the benefit of capsaicin], but some will be skeptical." Still, he said, "it's intriguing," and warrants further study.

Norman Latov, MD, medical and scientific director of the Neuropathy Association and professor of neurology at Cornell University, both in New York, told Medscape that he anticipated postherpetic neuralgia becoming more of a problem as the population ages and becomes more vulnerable to outbreaks of zoster. The pain from this can range from annoying to overwhelming, he said.

Currently, Lidoderm, a lidocaine patch, is the only Food and Drug Administration–approved treatment for postherpetic neuralgia.

The study was supported by NeurogesX Inc.

AAN 55th Annual Meeting: Abstract SLB.003. Presented April 1, 2003.

Reviewed by Gary D. Vogin, MD

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