Pharm 24: Heart rhythm Flashcards
Antiarrhythmic classes
I: Na+ block
II: β adrenergic block
III: K+ block
IV: Ca+ channel blockers
Na+ channel blockers MOA
decrease automaticity in SA nodal cells by shifting the threshold to more positive potentials and decreasing the slope of phase 4 depolarization
Na+ blockers and defib
Higher voltages are needed
NA+ blockers action on ventricular myocites
Decrease Phase 0 velocity, decrease automaticity
Class 1A effects
Moderate Na+ Block (phase 0)
Prolonged repolarization
Class 1B effects
Mild Na+ Block (phase 0)
Shortned repolarization
Class 1C effects
Marked Na+ Block (phase 0)
No change in repolarization
Quinidine class /MOA
1A
Also anticholinergic by blocking K+ after M2 stimulation.
Can increase AV conduction speed
Qunidine metabolism
P450 (bc of this bad to give w/ digoxin)
Procainamide Class/MOA and uses
1A
Used for rentry tachycardia
No anticholinergic effects
Chronic procainimide therapy leads to
Lupus like syndrome
Procainimide kinetics
Acetylated to N-Acetyl-procainimide (NAPA)
This is a class III for some reason
Disopyramide MOA/class and use
1A Na+
Used for VTACH
Lidocaine MOA use and class
1B
Bind to open and closed channels
Use for Vtach
What class exhibits use dependent block
1B
Lidocaine side effects
NOT torsades
CNS effects mostly