Misuse of Topical Numbing Drugs Draw FDA Warning

While topical anesthetics, or skin-numbing products, serve a useful purpose, unsupervised use or misuse can cause life-threatening side effects. Available both by prescription and over-the-counter (OTC), topical anesthetics contain drugs like lidocaine, tetracaine, benzocaine or prilocaine that work by desensitizing the nerve endings near the surface of the skin. These products are typically used to relieve pain, burning and itching from a variety of medical conditions such as minor cuts and burns, insect bites and poison ivy, but have also gained widespread popularity in preparing for painful medical tests, including mammograms, and for cosmetic procedures such as laser hair removal, tattoos, and skin treatments.

The FDA has approved many products for these uses, however it is important that certain precautions be taken. Applying topical anesthetics for a medical procedure is usually done in a doctor’s office by a trained medical professional, but use of these products before a cosmetic procedure may lack professional supervision. Without this supervision, a patient may apply too much of the anesthetic to their skin, resulting in high levels of the anesthetic drugs leaching into the bloodstream, leading to serious side effects.

Thus was the case of two women, aged 22 and 25, who applied topical anesthetics to their legs to lessen the pain of laser hair removal. The women then wrapped their legs in plastic wrap, as they were instructed, to enhance the creams’ numbing effect. Both women had seizures, fell into comas, and subsequently died from the toxic effects of the anesthetic drugs. In these two cases, the topical creams were made in pharmacies and contained high amounts of lidocaine and tetracaine. The FDA has also received reports of serious and life-threatening side effects such as irregular heartbeat, seizures and coma, and slowed or stopped breathing following the use of these numbing products. These effects occurred in both children and adults and when the anesthetic drugs were used for both approved and unapproved conditions.

In February 2007, following the death of these two young women, the FDA issued an advisory warning consumers of the health risks associated with the use of topical anesthetics. In that advisory, the agency explained that some of the anesthetic drugs in these products can pass through the skin into the blood stream, and more will enter when the product is applied over a large area of skin, when it stays on the skin for a long time, and when the skin is covered after application. Anesthetic drugs may also pass into the blood stream if the skin is irritated or has a rash. The amount of the drug that can pass through the skin and enter the blood stream can also vary from person to person.

The FDA recently reiterated their warning about the potentially serious hazards of using topical anesthetics for relieving pain from conditions and medical tests. The statement released by the agency on January 16 especially targets women who use topical anesthetics containing lidocaine on large skin areas, covered with plastic wrap before undergoing mammogram screening. This second warning was likely prompted by the results of a recently published study in Radiology that suggested a topical analgesic was more effective than oral painkillers for women concerned about discomfort from mammography. Researchers found that women using lidocaine, spread over the breasts and chest wall and covered with plastic wrap for a total absorption time of about 45 minutes, reported significantly less discomfort than those using ibuprofen, acetaminophen, or a placebo.

The FDA is concerned that widespread use of this procedure will lead to an increase in adverse health effects associated with topical anesthetics. “Although no serious side effects were reported in this study, it was not large enough to evaluate whether uncommon but serious reactions could occur with this use,” the FDA warning reads. “FDA remains concerned about the potential for topical anesthetics to cause serious and life-threatening adverse effects when applied to a large area of skin or when the area of application is covered.”

The FDA recommends that women who are considering using lidocaine to ease the discomfort of mammograms talk with their health care provider about the risks, how to identify adverse reactions, what actions to take if a reaction should occur, and how to reduce the chances of adverse events. Some cosmetic or medical procedures may also require a degree of numbness that cannot be safely achieved with these products, in which case a different treatment would be more appropriate.

The advisory strongly urges women who use topical anesthetics to choose one approved by the FDA and one that contains the lowest dose of anesthetic drugs possible that will relieve the pain. Apply as little of the product to cover the affected skin area for the briefest period possible and never use on broken or damaged skin. Users should also avoid wrapping or covering the treated skin or applying heat from a heating pad. “When skin temperature increases, the amount of anesthetic reaching the blood stream is unpredictable and the risk of life-threatening side effects increases with greater amounts of lidocaine in the blood,” the FDA statement said.