Author(s): Drew A Rosielle MD
Background The Lidocaine Patch 5% is a topical analgesic developed to treat peripherally generated neuropathic pain. It is approved in the US for treating post-herpetic neuralgia (PHN). This Fast Fact reviews its mechanism of action, research data, and dosage information.
Mechanism of Action The lidocaine patch is believed to provide analgesia by reducing aberrant firing of sodium channels on damaged pain fibers directly under the patch. Less than 5% of the lidocaine is absorbed, an insufficient dose to cause systemic effects or local anesthesia (patients do not feel numb under the patch). It was initially expected that only superficial pain qualities would be affected by the patch; however there is evidence that non-superficial qualities of pain (e.g. “dull” or “deep” pain) are also diminished by the patch. Nociceptive pain generation (such as sensitivity to pinprick, or hot or cold painful stimuli) is not affected. Tachyphylaxis has not been formally investigated; case reports have indicated some individuals have used the patch successfully for over a decade.
Research Data Most of the research using the lidocaine patch, and all of the randomized, placebo-controlled trials, have been in neuropathic pain syndromes. It has shown modest (10-20 mm decrease in pain on the 100 mm visual analog scale) but significant efficacy in PHN in randomized, placebo-controlled trials. Due to its ease of use and lack of toxicity or drug interactions, it is being used much more widely than PHN. Multiple case-reports, open-label studies, and unpublished anecdotal reports have found the patch efficacious for a range of neuropathic conditions (e.g. diabetic neuropathy, post-surgical neuralgia), chronic low back pain, osteoarthritis, bony metastases, vertebral compression fractures, and on open decubitus ulcer beds. This latter practice is directly warned against by the manufacturer and there are no published data as to the patch’s safety when used on open wounds. Note: great caution is necessary in interpreting results of non-controlled clinical reports due to the high likelihood of a placebo effect.
Administration/Toxicity The lidocaine patch comes as a 10x14 cm adhesive patch containing 700 mg of lidocaine. A box of 30 patches costs approximately $175 USD. One to three patches, or only a portion of a patch, can be placed directly over painful areas. Due to concerns about systemic lidocaine toxicity, up to a maximum of 3 patches applied simultaneously for 12 hours a day has been approved. Onset of analgesia is within a few hours and patients should be able to determine whether the patch is helpful within a week. Some patients find that pain worsens when the patch is off for 12 hours or if it is left on for more than 18 hours, therefore extended dosing has been investigated. Several pharmacokinetic studies have shown that systemic lidocaine levels remain well within the safe range with doses of up to 4 patches on for 24 hours. Adverse reactions are rare, mild, and mostly topical (rash). The patch is contraindicated in advanced liver failure due to decreased clearance of lidocaine.
Summary The lidocaine patch 5% is a safe and modestly effective topical analgesic for post-herpetic neuralgia. Controlled trials are needed to determine its efficacy in the treatment of neuropathic and non-neuropathic painful conditions other than PHN.
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Fast Facts and Concepts are edited by Drew A Rosielle MD, Palliative Care Center, Medical College of Wisconsin. For more information write to: email@example.com. More information, as well as the complete set of Fast Facts, are available at EPERC: www.eperc.mcw.edu.
Version History: This Fast Fact was originally edited by David E Weissman MD and published in January 2006. Current version re-copy-edited in April 2009.
Copyright/Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Rosielle D. The Lidocaine Patch. Fast Facts and Concepts. January 2006; 148. Available at: http://www.eperc.mcw.edu/EPERC/FastFactsIndex/ff_148.htm.
Disclaimer: Fast Facts and Concepts provide educational information. This information is not medical advice. Health care providers should exercise their own independent clinical judgment. Some Fast Facts cite the use of a product in a dosage, for an indication, or in a manner other than that recommended in the product labeling. Accordingly, the official prescribing information should be consulted before any such product is used.
ACGME Competencies: Medical Knowledge, Patient Care
Keyword(s): Pain – Non-Opioids