W2, 6 Antiarrhythmic Drugs Flashcards
What is cardiac arrhythmia or dysrhythmia?
Classification of Cardiac arrhythmias
Action potential of cardiomyocytes (what happens in each phase?)
- Phase 0: Depolarization of the cardiomyocytes (Starts with influx of Na and Ca through there channels)
- Phase 1: Partial Repolarization due to the closure of Na channels
- Phase 2: The Plateau Phase (there is maintained depolarization due to continuous influx of Ca channels. By the END of this phase, Ca channels CLOSE and K ions begin to exit the cell)
- Phase 3: Repolarization of the heart muscle due to K efflux until the potential returns back to RMP
- Phase 4: Resting stage of the heart (Itβs where the heart is fully relaxed)
Classification of antiarrhythmic drugs
What drugs are under the class IA?
Quinidine, Procainamide, Disopyramide
Quinidine pharmacodynamics
Route of administration of Quinidine?
Well absorbed after oral administration, peak plasma levels in 60-90min
Quinidine: Bound or free? And half life?
~90% bound to plasma proteins, which prolongs the drug half life (5-12hr)
How is Quinidine metabolized & excreted?
Metabolized in the liver (by P450 enzymes) and excreted in urine.
Quinidine Indications
- Ventricular and supraventricular tachyarrhythmia
- Antimalarial
(Note: Quinidine use in arrhythmia is much less now because of its severe cardiac and systemic toxicity)
Quinidine Adverse Effects?
MOA of Procainamide?
Same as quinidine
How does Procainamide differ from Quinidine?
- It is Minimally bound to plasma proteins (~ 20%)
-Compared with quinidine, it has less anticholinergic activity
Whatβs the half life of procainamide
half-life 3-4 hr
Metabolism of procainamide
Indications of procainamide
Used for ventricular and supraventricular arrhythmias
Whatβs the effect of prolonged therapy with procainamide?
Prolonged therapy leads to lupus-like syndrome (disappears upon drug withdrawal)
MOA of Disopyramide?
Same as Quinidine
Disopyramide is mainly used for β¦ ?
Used mainly for ventricular tachyarrhythmias
When to prescribe Disopyramide?
Reserved for patients who are intolerant or unresponsive to quinidine or procainamide
side effects of disopyramide?
What drugs are under the Class IB ?
Lidocaine, Mexiletine, Phenytoin
Class IB drugs are used in β¦ ?
Used in ventricular, not supraventricular, arrhythmia
(like disopyramide)
MOA of class IB?
Route of administration of Lidocaine (Lignocaine)?
Lidocaine is given through i.v.or i.m
Why Lidocaine is not given orally ?
What is the half life of Lidocaine?
Short half-life (1.5-2hr)
How is Lidocaine metabolized & excreted?
Metabolized in liver
excreted in urine
Lidocaine-Indications
Lidocaine adverse effects
Rare but serious side effects such as:
β’ Nausea, vomiting and anorexia
β’ CNS effects: drowsiness, disorientation, ataxia, muscle twitching, convulsions
β’ Impaired hearing
β’ Respiratory arrest
β’ Bone marrow depression, agranulocytosis
Mexiletine side effects
Side effects: tremors and nausea
What drug is analog of lidocaine, but it is effective orally?
Mexiletine (Used in ventricular arrhythmias, mostly used as an adjunct to other drugs)
Anticonvulsant agent with limited use in the treatment of arrhythmias
Phenytoin
Phenytoin (slide)
What drugs are classified under IC?
Flecainide, Propafenone
MOA of class IC?
Route of administration of class IC?
Given i.v. or orally