Lidocaine-d10 is intended for use as an internal standard for the quantification of lidocaine by GC- or LC-MS. Lidocaine is an inhibitor of voltage-gated sodium channels (Navs) and a local anesthetic. It inhibits Nav1.2 (Ki = 11 µM), adult and neonatal Nav1.5 (IC50s = 380.1 and 360 µM, respectively), and Nav1.7 and Nav1.8 channels (IC50s = 450 and 104 µM, respectively) expressed in Xenopus oocytes. Topical administration of lidocaine (1-2%) reduces escape behavior in a rhesus monkey model of noxious electrical cutaneous pain. Formulations containing lidocaine have been used as local and regional anesthetics.