Category: membrane
Nav1.x voltage-gated Na+ channels generate the action-potential upstroke. Pharmacology blocks the channel in its open or inactivated state, preferentially silencing rapidly-firing neurons (use-dependent block). Anticonvulsants (phenytoin, carbamazepine, oxcarbazepine, eslicarbazepine, lamotrigine, lacosamide, zonisamide) raise the seizure threshold by slowing recovery from inactivation. Local anesthetics (lidocaine, bupivacaine, ropivacaine, articaine, mepivacaine) achieve regional sensory block by depolarization-induced channel binding from inside the membrane; cardiotoxicity is dose-dependent (bupivacaine highest — racemic mix risk, levobupivacaine + ropivacaine were developed to reduce CV risk). Topical surface anesthetics (benzocaine, pramoxine) have the same fundamental MOA but stay extracellular. Methemoglobinemia is a benzocaine + prilocaine specific risk.