Journal of dental research
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Recent experiments are reviewed to present a current view of the mechanisms of conduction block by local anesthetics. Local anesthetics block the sodium channels whose opening causes the rising phase of the action potential. ⋯ This site is only available to charged compounds when the gate of the channel is open. In contrast, uncharged compounds (including the free base form of local anesthetics) appear to reach the site through the membrane's lipid interior, bypassing the channel "gates." Anesthetics blocking the gate of the channel can either enhance or inhibit the normal inactivation mechanism of the sodium channel, depending on the particular anesthetic.
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Local anesthetic agents may be classified according to their intrinsic anesthetic potency and duration of activity. Procaine and chloroprocaine are relatively weak, short-acting drugs. Lidocaine, mepivacaine, and prilocaine represent agents of intermediate potency and duration of action. ⋯ The central nervous system is most susceptible to the toxic effects of local anesthetic agents. Signs and symptoms of CNS excitation followed by depression are the most common manifestations of local anesthetic toxicity. Cardiovascular depression may also occur following administration of excessive doses of local anesthetic agents or following high spinal or epidural anesthesia.