capasacin research for pain

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Capsaicin Patch Eases Postherpetic Neuralgia Pain - Larry Schuster

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

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.

Reviewed by D. Vogin, MD

Larry Schuster is a freelance writer for Medscape.