Local anesthetics are used widely to provide anesthesia via local subcutaneous (SC) injection; topical application to skin and mucous membranes; and epidural, spinal, and regional nerve blocks. In addition, lidocaine (See Cimetidine and Other H2 Blockers) is used IV as an antiarrhythmic agent, and cocaine (See Chlorates) is a popular drug of abuse. Commonly used agents are divided into two chemical groups: ester-linked and amide-linked (Table II–2).