How can a drug block sodium channels without stopping every normal spike? · Grey Matter

Drugs such as carbamazepine bind the voltage-gated sodium channel mainly in its inactivated state, the brief state it enters after opening for each spike.

How can a drug block sodium channels without stopping every normal spike?

Drugs such as carbamazepine bind the voltage-gated sodium channel mainly in its inactivated state, the brief state it enters after opening for each spike. A neuron firing at an ordinary rate spends little time with its channels inactivated, so little drug binds; a neuron firing in a fast burst keeps its channels cycling through that state, the drug accumulates on them and fewer are ready for the next spike. The result, called use-dependent block, trims the long high-frequency runs that seizures are made of while leaving normal firing nearly intact.