title: Toxicity of topical lidocaine applied to the breasts to reduce discomfort during screening mammography.
abstract: BACKGROUND
  We measured the effect of 30 milliliters (mL) of 4% lidocaine gel on the breasts and chest wall of healthy women covered for 1 h on plasma concentrations of lidocaine and its principal metabolite, monoethylglycinexylidide (MEGX), electrocardiogram (EKG) results, and adverse events.
  
  
  METHODS
  This institutional review board-approved, prospective, open-label study complied with the Health Insurance Portability and Accountability Act (HIPAA). The study evaluated 10 healthy women aged 42-75 years with 30 mL of 4% lidocaine gel on the skin of the breasts and chest wall covered for 1 h. Cardiac and neurological assessments were performed and blood was drawn for lidocaine and MEGX levels at baseline and 1/2, 1, 2, 3, 4, 6, and 8 h after application. EKGs were performed before application and at 3 h. Subjects provided informed written consent. Primary and secondary outcomes were plasma concentrations of lidocaine and MEGX and frequency of adverse events, respectively. Statistical analysis included paired t-tests for EKGs and repeated measures regression for vital signs.
  
  
  RESULTS
  No lidocaine was detected in the blood of 9 of 10 subjects. One subject had low plasma concentrations of lidocaine just above the level of detection the first 4 h after application only. No MEGX was detected. Mean decrease in heart rate was likely multifactorial.
  
  
  CONCLUSIONS
  Thirty mL of 4% lidocaine gel on the breasts and chest wall covered for 1 h in healthy women resulted in plasma concentrations of lidocaine and MEGX well below therapeutic or toxic levels and no clinically significant adverse events.
authors.affiliation: Radiation Oncology, St. Luke's Mountain States Tumor and Medical Research Institute, United States of America.
authors.forename: Colleen K
authors.initials: CK
authors.lastname: Lambertz
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Johnson
authors.forename: Paul G
authors.initials: PG
authors.lastname: Montgomery
authors.forename: James R
authors.initials: JR
authors.lastname: Maxwell
authors.forename: Stefanie J
authors.initials: SJ
authors.lastname: Fry