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Local anesthesia is the condition that results when sensory transmission from a local area of the body to the central nervous system (CNS) is blocked. The local anesthetics constitute a group of chemically similar agents that block the sodium channels of excitable membranes. Because these drugs can be administered by topical application or by injection in the target area, the anesthetic effect can be restricted to a localized area (e.g., cornea, arm, foot). Even when these drugs are given in the vicinity of the spinal cord, it is still considered a form of local anesthesia because only a specific level of cord impulse transmission is blocked. When given intravenously, however, these drugs can have effects on other tissues.

Local anesthetics are used for a variety of purposes, including localized surgical procedures, labor and delivery, and joint manipulations. They can also be used for short-term pain relief in conditions such as tendonitis or in long-term situations such as pain associated with cancer. Table 16–1 presents some of the methods of delivery of local anesthetics and the common clinical uses of each method.

Table 16–1. Methods of Delivery and Clinical Uses of Local Anesthetics

Most local anesthetics in current use are esters or amides. In addition, they are amines with the ability to bind a proton (H...

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