Local anesthesia/anesthetics metabolism

Amide-type agents include articaine, lidocaine, bupivacaine, prilocaine, mepivacain and ropiva-caine. These are metabolized in the liver by microsomal enzymes with amidase activity. The amide group is preferred for parenteral and local use. If by accident rapidly administered intravascularly these agents, especially bupivacaine but also lidocaine, can produce serious and potentially lethal adverse effects including convulsions and cardiac arrest. They can more easily accumulate after multiple administrations. Intravenous lidocaine is sometimes used for regional anesthesia, for infiltration procedures, for the induction of nerve blockade and for epidural anesthesia. However, it is also used as an antiarrhythmic. Bupivacaine is a long-acting local anesthetic used for peripheral nerve blocks and epidural anesthesia. 

Short-acting (0.5 to 1 horn)—ester, first synthetic local anesthetic, relatively safe because of rapid metabolism in the plasma, fast onset-short duration, not good for topical anesthesia Ester, only local anesthetic that is a vasoconstrictor, only local anesthetic that produces euphoria, used by ENTs for surgical procedures because it reduces pain and controls bleeding Long-acting—Ester, used for spinal anesthesia and topical... 

Chloroprocaine (nesacaine), an ester local anesthetic, is a chlorinated derivative of procaine with rapid onset, short duration of action, and reduced acute toxicity due to rapid metabolism (plasma tj 25 seconds). A higher-than-expected incidence of muscular back pain following epidural anesthesia with 2-chloroprocaine has been reported this back pain is thought to be due to tetany in the paraspinus muscles, which may be a consequence of binding by the EDTA included as... 

Tetracaine (pontocaine), a long-acting amino ester, is significantly more potent and has a longer duration of action than procaine. Tetracaine may exhibit increased systemic toxicity because it is more slowly metabolized than the other commonly used ester local anesthetics. It is widely used in spinal anesthesia when a drug of long duration is needed. Tetracaine also is incorporated into several topical anesthetic preparations. Tetracaine is rarely used in peripheral nerve blocks because of the large doses often necessary, its slow onset, and its potential for toxicity. 

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