OTC Transdermal Analgesic Patches in Pain Management

Donna M. Lisi, PharmD, BCPS, BCPP, BCGP, BCACP

Disclosures

US Pharmacist. 2019;44(3):15-21. 

In This Article

Lidocaine

Lidocaine is a local anesthetic that acts by blocking voltage-gated sodium channels within the neuronal cell membrane. These channels are both increased and dysfunctional in patients with peripheral nerve damage, leading to chronic neuropathic pain. Lidocaine binds to the defective receptors, thereby blocking abnormal ectopic discharges. This results in the interruption of the transmission of the pain signal.[16] These damaged nerve cells can lead to the sprouting of abnormal nerve fibers, which may lead to hyperirritability. Lidocaine is believed to decrease sympathetic nerve sprouting.[16] It may also slow peripheral nociceptor sensitization and central hyperexcitability.[6]

Most studies involving the use of lidocaine for pain management have been conducted using the 5% lidocaine patch (Lidoderm, Endo Pharmaceuticals, Inc.), which is available only by prescription. Data for this more potent lidocaine preparation are conflicting. Even for this higher strength lidocaine patch, there is a lack of efficacy data from head-to-head comparison trials for neuropathic pain. The trials that are available are small and of limited quality.[17]

Most OTC patches contain 4% lidocaine. Even when the 5% patch is utilized, systemic absorption is low.[3] Oni and colleagues compared the blood levels achievable from five commercially available lidocaine preparations (three OTC lidocaine 4% patches, two prescription lidocaine 5% patches, one compounded lidocaine patch) and found that there were significant interindividual differences.[18] The OTC preparations produced the highest lidocaine and metabolite, monoethylglycinexylidide (MEGX), levels compared with the other preparations. The authors warned that although topical lidocaine products are safe, some patients may experience unpredictably high absorption, leading to elevated blood levels.[18] This is important since lidocaine has both antiarrhythmic and proarrhythmic properties.[19] Toxicity occurs at lidocaine levels greater than 5 mcg/mL.[20]

Castro and Dent conducted a double-blind placebo-controlled trial involving 87 patients with back pain or arthritis who were administered either an OTC transdermal patch containing 3.6% lidocaine and 1.25% menthol, a 5% prescription lidocaine transdermal patch, or a placebo patch. The OTC product was found to be noninferior to the prescription lidocaine transdermal patch in terms of efficacy, side effects, and impact on quality of life. It was also found to be better than the placebo patch with respect to efficacy and the patient's ability to engage in general activity and work. Both lidocaine patches were manufactured by JAR Laboratories, which partially funded this research.[21]

"Due to their good safety profile, low incidence of systemic effects, and lack of drug-drug interactions, lidocaine patches may be especially useful for the management of focal neuropathic pain (with or without allodynia) in older adults."

The treatment duration for OTC lidocaine patches is up to 7 days. The patches can be used every 6 to 8 hours as needed, not to exceed three applications within 24 hours.[14]

Due to their good safety profile, low incidence of systemic effects, and lack of drug-drug interactions during topical exposure, lidocaine patches may be especially useful for the management of focal neuropathic pain (with or without allodynia [heightened pain sensitivity to otherwise innocuous stimulation]) in older adults.[6]

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