Sodium channel blocker
Sodium channel blockers are drugs which impair the conduction of sodium ions (Na+) through sodium channels. == Extracellular == The following naturally-produced substances block sodium channels by binding to and occluding the extracellular pore opening of the channel: Alkaloids: Saxitoxin (STX) Neosaxitoxin (NSTX) Tetrodotoxin (TTX) == Intracellular == Drugs which block sodium channels by blocking from the intracellular side of the channel include: Local anesthetics: lidocaine Class I antiarrhythmic agents Various anticonvulsants: phenytoin, oxcarbazepine (derivative of carbamazepine) == Unknown mechanism == Calcium has been shown to block sodium channels which explains the effects of hypercalcemia and hypocalcemia.