Lidocaine belongs to a class of local and topical anesthetic medications. As lidocaine causes a temporary numbness or loss of sensation when injected in the tissues, it is used as a local anesthetic and in the treatment of pain. When given intravenously, lidocaine is also an antiarrythmic agent, capable of correcting some ventricular arrythmias of the heart. The lidocaine patch is a topical treatment that is especially helpful in the treatment of pain associated with postherpetic neuralgia, a condition that can occur after infection with the herpesvaricellazoster (shingles) virus. Additionally, the lidocaine patch is sometimes used in the treatment of some chronic forms of nerve pain such as the pain associated with fibromyalgia.
Purpose
The lidocaine patch relieves pain and discomfort by blocking signals sent to nerve endings in the skin. Almost 20% of the one million Americans who develop shingles yearly experience long-term pain after the infection has resolved. People over age 60 are especially prone to postherpetic neuralgia.
Description
The lidocaine patch is composed of an adhesive material containing 5% lidocaine that is applied to a polyester felt backing. When it is applied to the skin, lidocaine is released into the epidermal and dermal layers of the skin, reducing pain at the site of the dysfunctional nerves damaged by the prior herpes zoster infection. The lidocaine patch provides pain reduction without numbness of the affected skin.
In the United States, the lidocaine patch is sold under the name of Lidoderm.
Recommended dosage
The lidocaine patch is available in varying doses. Patches are applied directly to healthy, non-broken skin close to the source of pain or discomfort. Patients may typically apply up to three patches at one time. However, patches should not be worn longer than 12 hours in a 24-hour period. Patches can be cut into smaller pieces before removing the release liner and applying to the skin. Clothing may be worn over the applied patch.
If a dose is missed, it should be taken as soon as possible. However, if it is almost time for the next dose, then the missed dose should be skipped. More patches than are instructed by the prescribing physician should never be applied.
Precautions
Lidocaine may not be suitable for persons who have had a past reaction to any local anesthetic. Patients should discuss past adverse reactions to anesthetics with their physician before using the lidocaine patch. The lidocaine patch may also not be suitable for persons with a history of severe liver disease. Additionally, the lidocaine patch should be used with caution in persons receiving antiarryhthmic drugs.
Hand-washing is important after handling or applying the lidocaine patch. Contact with eyes should be avoided. The zipper pouch containing the lidocaine patches should be completely closed after opening, as the patches will lose potency if allowed to dry. Patches can be cut with scissors to the size and shape necessary to fit facial areas, but care should be used not to allow the material in the lidocaine patch to enter the eye. The lidocaine patch should never be chewed or ingested, or used to relieve pain inside the mouth.
Side effects
As only minute amounts of lidocaine enter the bloodstream from the patch, side effects are few. Most patients tolerate normal use of the lidocaine patch well, but some patients may experience usually mild side effects. Localized tingling may occur. If a rash or burning sensation occurs after application, the patch should be removed and not reapplied until the irritation subsides. If any symptom becomes uncomfortable, patients should consult the prescribing physician.
Some patients may be allergic to topical lidocaine and the lidocaine patch. Medical treatment should be sought immediately if any of the following symptoms occur:
Other less common side effects of the lidocaine patch may be serious, potentially indicating that too much medication is being absorbed into the body. A patient should seek medical treatment if experiencing:
As the lidocaine patch is topical treatment and only minute amounts of the drug are absorbed into the bloodstream, interactions with other drugs are few. The lidocaine patch may have rare negative interactions with digoxin (Lanoxin) or any medications for irregular heartbeats. Some antibiotics, antidepressants, and monoamine oxidase inhibitors (MAOIs) may adversely react with the lidocaine patch or lessen its effectiveness.
PERIODICALS
Alper, B. S., and P. R. Lewis. "Treatment of Postherpetic Neuralgia: A Systemic Review of the Literature." Journal Fam. Pract. (2002): 51: 121–8.
Argoff, C. E. "New Analgesics for Neuropathic Pain: The Lidocaine Patch." Clin. Journal Pain (2000): 16: S62–66.
Watson, C. P. "A New Treatment for Postherpetic Neuralgia." New England Journal Med. (2000): 343: 1563–65.
OTHER
"Lidocaine Patch Effective in Relieving Nerve Pain After Shingles." The Doctors'Guide. June 4, 1999. May 13, 2004 (June 1, 2004). <http://www.pslgroup.com/dg/102db6.htm>.
