The purpose of this study is to test the hypothesis that one-time application of 4% lidocaine gel (TOPICAINE) on the skin of the breasts and chest wall as recommended for pre-medication to reduce discomfort during screening mammography does not result in adverse effects, electrocardiogram (EKG) changes, or systemically toxic plasma concentration of lidocaine or its principal metabolite, monoethylglycinexylidide (MEGX).