Skin numbing drugs such as lidocaine, tetracaine, benzocaine, and prilocaine have been linked to serious and life-threatening side effects when used improperly. According to a Food & Drug Administration (FDA) warning issued last week, the agency is especially concerned about the danger posed by the drugs when they were used on women to reduce the discomfort of mammograms.
These skin numbing drugs are available as creams, ointments and gels, and work by blocking pain sensation in the skin. When applied to the skin surface, they can be absorbed into the blood stream. The FDA warned on Friday that when used improperly, these skin numbing drugs may cause life-threatening side effects, such as irregular heartbeat, seizures, breathing difficulties, coma, or even death.
The new FDA warning on skin numbing drugs follows a February 2007 health alert prompted by the deaths of two women who were treated with the products to lessen leg pain following a hair removal procedure. At the time, the FDA warned that an excessive amount of the drugs’ active ingredients could pass into the blood stream when the products were applied over a large area of skin, when it stays on the skin for a long time, and when the skin is covered with plastic wrap after application of the product. Under these circumstances, the amount of anesthetic medication that reaches the blood stream is unpredictable, and may be high enough to cause life-threatening adverse effects.
When skin numbing products are used to lessen mammography pain, they are applied to a wide area of skin, and the area is covered in plastic. The FDA warning said that even though a recent study published in the journal Radiology had shown the numbing cream lidocaine to be more effective at treating mammography pain than acetaminophen or ibuprofen, it is concerned that serious side effects could occur when it and similar products are used this way. While the Radiology article reported no serious or life-threatening side effects among mammography patients treated with lidocaine, the FDA pointed out that the study was small and it is possible that a larger study might show different findings.
The FDA advised patients to talk with their health care professional if they are considering using a topical anesthetic before a mammogram. The agency also made the following recommendations to patients who use lidocaine cream and other skin numbing agents:
- use a topical anesthetic that contains the lowest strength, and amount, of medication that will relieve the pain;
- apply the topical anesthetic sparingly and only to the area where pain exists or is expected to occur;
- do not apply the topical anesthetic to broken or irritated skin;
- ask their healthcare professional what side effects are possible and how to lower their chance of having life-threatening side effects from anesthetic drugs; and
- be aware that wrapping or covering the skin treated with topical anesthetics with any type of material or dressing can increase the chance of serious side effects, as can applying heat to the treated area while the medication is still present.