Jun 8, 2017Skin Deep
An April report published by Allied Market Research titled, “World Analgesics Market-Opportunities and Forecasts, 2015-2022,” projects that the world analgesics market will reach $26.4 billion by 2022. Non-opioids, including topical (transdermal) analgesics, are believed to grow the fastest during this period. So if athletic trainers don’t know a lot about these products, now is a good time to get familiar.
Marketed for the treatment of musculoskeletal pain (myalgia), inflammation, and joint pain (arthralgia), topical analgesics come in creams, gels, balms, sticks, foams, sprays, and patches. The most common forms contain counterirritants (capsaicin, camphor, and menthol), salicylates, or herbal/homeopathic preparations, with many of these ingredients being combined, such as methyl salicylates. Although many of these products produce either a cooling or warming sensation, there is little evidence that any provide temperature changes in deeper tissue (muscle) or clinically meaningful surface temperature changes.
Topical analgesics are often recommended for pain relief because they avoid the first pass metabolism associated with the gastrointestinal tract and may lower the systemic side effects and risks associated with organ and tissue toxicity. Their ease of use, convenience, and painless administration are also highlighted as advantages when compared to oral analgesics. However, no product can treat every type of pain or tissue as the causes, durations, and manifestations are usually different.
So how do they work? Topicals deliver medication directly to the application site, which is usually the perceived location of pain. Counterirritants (capsaicin, menthol, and camphor) are designed to excite and subsequently desensitize nocioceptive sensory neurons, whereas salicylates and herbal remedies are usually designed to decrease the inflammatory process by inhibiting the synthesis of prostaglandin and reducing inflammatory mediators that activate nocioceptors. Both also help block the transmission of pain messages along the neural pathways via the application process, as creams, gels, and balms require rubbing to apply.
Evidence is mounting in support of pain relief by topical analgesics — particularly low-concentration capsaicin and non-steroidal anti-inflammatories (salicylates) — for both acute and chronic musculoskeletal pain in athletes. Capsaicin may also be helpful for patients who are unresponsive or intolerant to other treatments. Support for pain relief herbal preparations has been demonstrated, as well. One study found topical arnica was able to decrease the perception of pain 72 hours after downhill running.
The application of topicals varies based on product and target market, but it’s important to always follow label instructions. Do not apply topicals to damaged or irritated skin or mucous membranes, and don’t bandage the application area too tightly. Athletes who have an aspirin sensitivity or allergy should be advised that products containing methyl salicylate or other salicylates may cause an allergic reaction. If skin itches, burns, stings, or turns red when applying a topical, athletes should stop using the product. The FDA recommends against using heating pads, heating lamps, hot or cold water bottles, or ice packs along with topical ointments as these can magnify the sensations of warming and cooling. Finally, wash hands after application to avoid getting the product in the eyes, nasal cavity, or mouth.
Also, remember that more is not better. Applications of topicals should be in small amounts (1 to 1.5 grams or a quarter to half dollar size), three to four times a day.
Topical analgesics are very popular and have been demonstrated to be effective for both acute and chronic musculoskeletal pain. As our understanding of pain evolves, newer topical analgesics that are tailored for specific pain processes and contained within mediums that increase penetration and/or absorption may enhance their future use in sports medicine.
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