The study find that the topical analgesic patches offer both convenience and consistent drug administration.  But Among the active ingredients available in these products are lidocaine; capsaicine, methyl salicylate, and menthol. There is a paucity of studies about the efficacy and safety of these medications. Studies that are available are often of poor quality. While generally considered safe when used according to product labeling, these medications can also be associated with adverse effects.

Safety of these medications

Pharmacists need to be familiar with the available evidence regarding the use of these products in order to help patients safely self-medicate. According to the latest report from the CDC; 20.4% of adults in the United States experience chronic pain. Among the therapeutic options for the management of pain are OTC or nonprescription topical analgesic patches.

In the February 1983 Federal Register, the FDA published; the tentative final monograph on OTC external analgesic drug products, which included patch, plaster; and poultice dosage forms. In July 2003, the FDA reopened the administrative record for the rulemaking for OTC external analgesic to include more recent data on these medications.

The tentative final monograph

Patches offer advantages over oral analgesic medications . However; drawbacks to the use of topical analgesics exist, including local irritation or skin sensitization; interindividual variability of skin properties that can affect absorption (e.g., adult vs. pediatric patients); limited availability of medications that be deliver via this route of administration; inappropriateness of the topical route of administration for patients with decrease peripheral blood flow (e.g., shock); and cost.

Another caveat is that some transdermal products contain metallic backings, which can lead to excessive burns and local tissue damage if the patch is not remove prior to undergoing an MRI scan. Similarly; reports of severe burns have occurred when these products are use in conjunction with a heat source such as a heating pad or sauna or when the patch has been positioned over an implantable cardioverter defibrillator.

Drug-safety communication

In 2012, the FDA issued a drug-safety communication stating that rare cases of serious burns (including second- and third-degree burns) have occurred with the use of OTC topical muscle and joint pain relievers. This problem was seen particularly with the use of products containing menthol as the single active ingredient or products containing both menthol and methyl salicylate (MS), in concentrations greater than 3% menthol and 10% MS .

Few cases were described involving the use of capsaicin-containing products. Healthcare professionals should counsel patients about how to use these products appropriately, including discussing the risk of serious burns. These medications can also cause acute toxicity in children even when ingested in small amounts.

The barrier function of the skin is incomplete in premature infants, putting them at increased risk from dermal exposure. Medicated patches may retain up to 95% of the initial total amount of drug, even after the duration of use has passed, which can pose a risk to curious, unattended children.