Antiarrhythmic Drugs Flashcards
What are the 2 mechanisms of tachyarrhythmias?
Abnormality in impulse generation aka “automatic tachycardias”
abnormality in impulse conduction aka “reentrant” tachycardias
How do most antiarrhythmic drugs work?
by modulating the activity of ion channels in the plasma membranes
Generally, AADs alter cardiac rhythm by altering…
- maximum diastolic potential of PPM cells
- the rate of phase 4 depolarization
- the threshold potential
- the action potential duration
Class I antiarrhythmics
Na+ channel blocks
Prototype: Procainamide, Lidocaine, Flecainide
Depress Na+ conduction in ischemic tissue greater than normal tissue
Class II antiarrhythmics
Beta adrenergic receptor antagonists
Prototype: Propranolol
Class III antiarrhythmics
K+ channel blockers
Prototype: Amiodarone
Class IV antiarrhythmics
Ca+ channel blockers
Prototype: Verapamil
Misc AADs include
Adenosine, Mg, K
Class IA prototype? MOA?
Procainamide
Inhibits Na+ channel, inhibits K+ current
Effects of Procainamide
Slows conduction velocity and PPM rate
Clinical applications for procainamide?
can be used to tx most atrial and ventricular arrhythmias
2nd choice for most sustained V arrhythmias associated with acute MI
Procainamide toxicities?
torsades de pointes in pts with renal failure
hypotension, long-term therapy produces reversible lupus related sxs
Disopyramide is also a class 1A Na+ channel blocker, how does it differ from Procainamide? What about Quinidine?
longer duration of action, toxicity includes antimuscarinic effects and HF
toxicity includes cinchonism (tinnitus, HA, GI disturbances) and thrombocytopenia
Class IB prototype? MOA?
Lidocaine
highly selective Na+ channel blocker
minimal effect in normal tissue
Clinical application for Lidocaine?
ventricular arrhythmias post MI
Lidocaine toxicities?
reduce dose in pts with HF or liver disease
neurological sxs: CNS sedation or excitation
Mexiletine is also a Class IB AAD, how does it differ from Lidocaine?
oral med
longer duration of action
Class IC prototype? MOA?
Flecainide
Na+ channel blocker
Effects of Flecainide?
dissociated from channel with slow kinetics, no change in action potential duration
Clinical application of Flecainide?
supraventricular arrhythmias in pts with normal heart, do not use in ischemic conditions (post MI)
Flecainide toxicities?
pro arrhythmic
Class II antiarrhythmics are useful in the treatment of…
supraventricular and ventricular arrhythmias precipitated by sympathetic stimulation
Class II prototype? MOA?
Propranolol
Beta-Adrenoceptor blocker