What are the mechanisms of action and pharmacokinetics of sodium channel blockers?

Updated: Jan 28, 2020
  • Author: Juan G Ochoa, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

The firing of an action potential by an axon is accomplished through sodium channels. Each sodium channel dynamically exists in the following 3 states:

  • A resting state, during which the channel allows passage of sodium into the cell

  • An active state, in which the channel allows increased influx of sodium into the cell

  • An inactive state, in which the channel does not allow passage of sodium into the cell

During an action potential, these channels exist in the active state and allow influx of sodium ions. Once the activation or stimulus is terminated, a percentage of these sodium channels become inactive for a period known as the refractory period. With constant stimulus or rapid firing, many of these channels exist in the inactive state, rendering the axon incapable of propagating the action potential.

AEDs that target the sodium channels prevent the return of these channels to the active state by stabilizing them in the inactive state. In doing so, they prevent repetitive firing of the axons (see the image below).

Some antiepileptic drugs stabilize inactive config Some antiepileptic drugs stabilize inactive configuration of sodium (Na+) channel, preventing high-frequency neuronal firing.

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