Pharm - Antiarrhythmic Drugs Flashcards
Most antiarrhythmic agents that target K channels target ___
IKR
Antiarrhythmic drugs can cause ___ but not treat them. These are best treated with ___
Bradyarrhythmias
Implantable devices
Vaughan Williams classification of Antiarrhythmic drugs
I: Na channel blockers (IA, IB, IC)
II: beta receptor blockers
III: K channel blockers
IV: Ca channel blockers
___ has the least effect on Phase 0.
___ has the most effect on Phase 0.
___ also increases the AP duration because ___
- IB
- IC
- IA, side effect: blocks IKR and IKS channels (IB, IC do not)
Avoid class ____ in patients with structural damage (e.g. Post-MI)
IC
Class IA examples:
Quinidine
Procainamide
Disopyramide
Class IB examples:
Lidocaine
Mexiletine
Phenytoin
Class IC examples:
Flecainide
Propafenone
Class ___ has the lowest affinity for Na channels
Class __ has the highest affinity for Na channels
IB
IC
Affinity and kinetics of Class I drugs
Affinity: IC>IA>IB
Kinetics: IB>IA>IC
All class I antiarrhythmic decrease the ___ and reduce the ___
Decrease the upstroke velocity (phase 0) and reduce the amplitude of the cardiac AP
*this may depress conduction velocity and slow impulse propagation
Class IA
Anti-muscarinic
May enhance conduction through the AV node
-also blocks IKR channels (class III effect)
-prolongs QT interval
-increases risk of torsades de pointes
Class IA agents list:
Detailed
- Quinidine (rarely used due to toxicity, blood cos CYP2D6, metabolized by CYP3A4)
- Procainamide (IV only; most used, half life is 3-4 hrs, adverse effect includes lupus like disorder)
- Disopyramide (avoid in heart failure, negative inotropic effect)
Uses of class IA drugs
Atrial and ventricular tachyarrythmias
Uses for class IB agents
Ventricular arrhythmias ONLY
Class IB agents list:
Detailed
- Lidocaine (very effective for post-MI ventricular arrhythmias, ineffective for most supraventricular arrythmias, neurological side effects, less cardiotoxic than IA or IC)
- Mexiletine (orally active form of lidocaine)
- Phenytoin (antiepileptic drug)
Class IC drugs have no effect on ___ and are used for ___
AP repolarization
-supraventricular arrhythmias or life threatening ventricular arrhythmias in patients without heart disease
Class IC agents list:
Detailed
- Flecainide (supraventricular arrhythmias, NOT for previous MI, metabolized by kidney and CYP2D6)
- Propafenone (supraventricular and ventricular tachycardias, NOT for previous MI, hepatic metabolism, also blocks cardiac beta adrenergic receptors as in class II)
___ are shown to reduce mortality in HF patients
Beta Adrenergic receptor blockers
Class II
Class II examples:
- Esmolol
- Metoprolol
- Atenolol
- Propranolol
Uses for class II
- Sinus tach
- Supraventricular and ventricular tachyarrhythmias
- A fib
- Stable angina
- Hypertension
- HF
- Reduces mortality following acute MI and in HF
Class II agents list:
Detailed
- Propranolol (nonselective, b1 and b2)
- Metoprolol (cardioselective, b1)
- Atenolol (same as metoprolol)
- Esmolol (same as metoprolol, IV only)
Atenolol can only be used in patients without ___
Bronchospasms
Class III drug list:
- Amiodarone
- Ibutilide
- Difetilide
- Sotalol
- Dronedarone
___ is the most common class III drug. It also blocks what?
Amiodarone
-Na, Ca, and Beta receptors
Dosing of amiodarone
Once daily due to long half life
Uses of dronedarone
Half life?
Side effects?
A flutter/fib after conversion to sinus rhythm
- half life is 13-19 hours
- no iodine so no thyroid probs, but does have hepatic tox
Sotalol is a class ___ drug but is also a ___
III
nonselective beta blocker
Ibutilide is a class ___ drug that also does what?
III
Enhances a slow inward Na current
*IV only
Class IV drugs
-2 subclasses
Dihydropyridines
-smooth muscle relaxation (antihypertensive and antianginal)
Non-dihydropyridines
-cardiac selective, slows HR and decreases contraction (antiarrhythmic and antianginal)
Class IV non-dihydropyridines list
Diltiazem
Verapamil
Other agents:
Adenosine
IV only
Acute termination of PSVT
Other agents:
Digoxin
Cardiac glycoside
Inhibits Na/K ATPase pump
Slows HR and conduction velocity
Increases ERP in AV node (vagomimetic)
