Magazine article Drug Topics

New Lidocaine Patch Targets Painful Shingles Complication

Magazine article Drug Topics

New Lidocaine Patch Targets Painful Shingles Complication

Article excerpt

Reaffirming the old saying that necessity truly is the mother of invention, a retired pharmacist has initiated the development of a newly approved product for post-herpetic neuralgia (PHN), a resulting complication of shingles.

In a desperate search for a remedy that would bring relief to his wife's painful and debilitating case of PHN, Harry Hind came up with the idea of applying a topical lidocaine solution to the affected area of his wife's back and then covering it with plastic wrap. His treatment might have been messy, but it worked. The idea went through several years of fine-tuning and eventually evolved into Lidoderm (lidocaine patch 5%, Endo Pharmaceuticals), one of only a few treatments specifically indicated for the condition.

The new product is expected to fill a therapeutic void since current treatment options for PHN include mostly systemic therapy with anticonvulsants such as gabapentin or tricyclic antidepressants (TCA)all of which have disadvantages, according to Bradley Galer, M.D. "The problem with gabapentin is that it takes two months to titrate to a dose that may be effective, and TCAs often produce drowsiness and cognitive side effects-especially in the elderly," noted Galer, a director at the Clinical Studies Institute for Education and Research in Pain and Palliative Care, Beth Israel Medical Center, New York City.

Although the transdermal product contains nothing new under the sun-just an old-time anesthetic-it's no ordinary patch, thanks to a novel delivery rate. So don't assume that any topical lidocaine can simply be substituted for this product. While lidocaine, delivered via other routes, produces the well-known anesthetic effects, Lidoderm is thought to produce analgesic effects without exerting the complete sensory block that results in numbness. "The patch delivers a predetermined, low level of lidocaine into the epidermal and dermal layers of the skin over a long period of time. This flux rate is crucial since it ensures that the amount of drug released is below anesthetic levels yet just enough to stabilize the damaged nerves and prevent them from shooting off erratic pain signals to the brain," explained Hind.

According to Galer, Lidoderm is effective in relieving pain associated with PHN in approximately 60% to 70% of patients. …

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