Na-channel inhibitors Flashcards
What are Class I drugs and what do they do?
Na channel blockers; Alters AP duration and kinetics of Na channel blockade
What are Class II drugs and what do they do?
Beta blockers; block SNS effects of the heart
What are Class III drugs and what do they do?
K channel blockers; prolongation of the effective refractory period
What are Class IV drugs and what do they do?
Calcium channel blockers; slows conduction where depolarization is calcium dependent
When do Na channel blockers act on the channel?
When the channel is in an inactivated state (elongates phase 0)
When do K channel blockers act on the cell
Slows efflux of K during phase 3, prolonging refractory time of the cell
When do Ca channel blockers act on the cell?
Slows influx of calcium (phase 1, 2 and 3) by blocking L-type channels
What do Na channel blockers affect nodal tissue?
Nodal tissue is dependent on calcium channels to depolarize
What channels do Na channel blockers typically block: Fast or Slow?
Fast Na channels
What do Class 1-A Na channel blockers do to ERP?
Increase ERP
What do Class 1-B Na channel blockers do to ERP?
Decrease ERP
What do Class 1-C Na channel blockers do to ERP?
Don’t change ERP
What are Na channel blockers typically used to treat?
Various tachycardias
What are Class II drugs (beta blockers) used to treat in arrhythmias?
Supraventricular arrhythmias, and reduce ventricular ectopic depolarizations and sudden death in MI patients
What are the observed effects of Beta blockers?
slow the heart rate, decrease the AV node conduction velocity (Increase PR interval), increase AV node refractory period, NO EFFECT ON VENTRICULAR CONTRACTION/REPOLARIZATION
