FDA warns against lidocaine for relieving mammography-related pain

The FDA has issued an advisory warning physicians and patients about potential health risks from topical anesthetic lidocaine used to reduce the discomfort of mammography.

The potential value of lidocaine was the subject of a study published in the September 2008 issue of Radiology (2008;248(3):765-771). Dr. Colleen K. Lambertz and colleagues at St. Luke's Mountain States Tumor Institute in Boise, ID, found in an evaluation of 418 women that nonprescription 4% lidocaine gel spread on the subjects' breasts, then covered with a plastic wrap before imaging, was significantly more effective than oral administration of acetaminophen or ibuprofen for reducing the discomfort of breast compression during mammography.

Lambertz reported that lidocaine produced a few minor side effects, but the FDA noted in a Jan. 16 advisory that the study was not large enough to evaluate whether uncommon but serious reactions could occur. The FDA expressed concern about the potential for topical anesthetics to cause serious and life-threatening adverse effects when applied to a large area of skin or an area that is covered.

In February 2007, the FDA issued Public Health Advisory: Life-Threatening Side Effects with the use of Skin Products Containing Numbing Ingredients for Cosmetic Procedures, which described the deaths of two young women who used topical anesthetics prior to laser hair removal.

Topical anesthetics work by blocking pain sensation in the skin, the FDA said. Some of the medication in a topical anesthetic can pass through the skin into the bloodstream. More of the medication will pass into the bloodstream if the topical anesthetic is applied over a large area of the skin, a large amount is applied, it is applied to irritated or broken skin, or the skin temperature increases.

Skin temperature can increase during exercise, when the skin is covered with a wrap, or with use of a heating pad. Under these circumstances, the amount of anesthetic medication that reaches the bloodstream is unpredictable and may be high enough to cause life-threatening adverse effects such as irregular heartbeat, seizures, breathing difficulties, and coma. Even death can ensue.

The FDA asked patients to consult with their physician if they consider using a topical anesthetic before a mammogram. The FDA recommended that patients and physicians follow these guidelines when a topical anesthetic is recommended:
• Use a topical anesthetic that contains the lowest amount possible 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
• Not apply the topical anesthetic to broken or irritated skin
• Patients ask their doctor what side effects are possible and how to lower their chance of having life-threatening side effects from anesthetic drugs
• Be aware that if wrapping or covering the skin with any type of material or dressing is recommended or considered, this can increase the chance of serious side effects, as can applying heat to the treated area while the medication is still present

For more information from the Diagnostic Imaging and SearchMedica archives:

Over-the-counter anesthetic reduces breast imaging painHologic bids $70 million for mammography cushion makerMammography vendors pursue better operability