Anti-Arrhythmia Drugs Flashcards
Procainamide
Function: Class 1-A: Na+ channel blocker. Reduces Vmax, increases AP duration, ERP
Usage: Broad spectrum anti-arrhythmic. Supraventricular and ventricular (esp. Vtach and Vfib)
Toxicity: Cardiac toxicity (suppression, arrhythmias), SLE-like syndrome,
Other: Chronic use no longer common in US.
Quinidine
Function: Class 1A: Na+ Channel Blocker. Reduces Vmax, increases AP duration, ERP. Has anti-muscarinic & K+ channel blocking properties
Usage: Chronic oral therapy for supraventricular arrhythmias (Afib, flutter, PSVT?) and tachycardias including Vtach
Toxicity: Diarrhea, Cinchonism (tinnitus, dizziness, headache). Low therapeudic index
Other
Lidocaine
Function: Class 1B: Sodium channel blocker. Shortens AP duration and ERP, decreases automaticity in His-Purkinje fibers.
Usage: Ventricular arrhythmias, particularly in surgery/ICU
Toxicity: Pretty safe but can lead to CNS depression (drowsiness, irritability, convulsions)
Other: IV admin, short half life. Mexiletine and Tocainide are longer acting, oral drug class 1B drugs for ventricular arrhythmias
Flecainide
Function: Class 1C: Na+ channel blocker. Large reduction in Vmax (slower rate of binding/unbinding) , little effect on ADP, ERP.
Usage: Used for supraventricular tachyarrythmias like Afib and Aflutter (maintain sinus rhythm).
Toxicity: increased potential for sudden cardiac death. Contraindicated in Post-MI
Other: Picmonic says 1C drugs are also used for Vtach, but in all cases are “last resort” drugs for refractory tachycardias.
Amiodarone
Function: Class III. High affinity K+ channel blockade plus 1A blockade of Na+ channels. Low affinity block of b-receptors and Ca++ channels.
Usage: Recurrent Vtach, Vfib (high dose). Atach in pts. resistant to other drugs (low dose)
Toxicity: Hypotension, Pulmonary fibrosis, photosensitivity, thyroid/liver dysfunction, headache/tremor/parasthesias
Other: Reduced mortality in chronic tx–> increased use relative to other class I drugs. Poor oral absrobtion and bioavailability.
Dronaderone
Function: Class III. Similar fx to amiadarone (K+ blockade) as well as high affinity for Na+ channels.
Usage: Afib, Vtach
Toxicity: Less toxic than Amiadorone
Dofetilide
Function: Class III Specific Ikr channel blocker. maintains sinus rhythm w/ atrial fib
Usage: Afib post MI
Toxicity: Prolonged QT leading to ventricular arrhythmia
Other: Similar drug: Ibutilide (converts Afib/Aflutter to sinus rhythm)
d,l- Sotalol
Function: Class II/III hybrid. B-adrenergic blockade (l-sotalol), K+ blockade (l,d sotalol). Prolongss APD, ERP. Decreases SA node automaticity & AV nodal conduction
Usage: Ventricular tachyarrhythmias, SVT’s including Afib.
Toxicity: Arrhythmias (prolonged QT), Vtach at high doses
Other: Low dose–> Beta blockade, High dose–> Both Beta-blockade and K+ blockade
Adenosine
Function: Class II (sort of). Inhibits cAMP in HCN (funny) channels, binds Kir channels hyperpolarizing diastolic membrane potential. SLOWS SA node firing, slows AV conduction
Usage: Acute conversion of AVRT’s. Vtach due to afterdepolarizations
Toxicity:
Other: Extremely rapid uptake, administered in bolus
Diltiazem
Function: Benzothiazepine. L-type Calcium Channel Blocker. Class IV Anti-arrhythmic. Increases ERP, slowing AV conduction, Slows SA automaticity.
Usage: Arrhythmias (supraventricular- PSVT, Afib/Aflutter), HTN,
Toxicity: hypotension. Contraindicated in slowed AV conduction and CHF.
Verapamil
Aciton: Phenylalkylamine. Cardioselective L-type Ca2+ channel blocker. Class IV Anti-arrhythmic (frequence dependent action)
Usage: HTN, Angina, Arrhythmias (PSVT, Afib/Aflutter)
Toxicity: Cardiac depression, constipation
Other: Strong cardiac blocking effect w/ weak smooth muscle blocking effect
Nifedipine
Action: Dihydropyridine. Vascular selective L-type Ca2+ channel blocker. Class IV anti-arrhythmic.
Usage: HTN, angina (Great for these), arrhythmias (Not very useful)
Toxicities: Hypotension, flushing, dizziness
Other: Strong vascular smooth muscle blocking effect w/ weak cardiac blocking
Propranolol
Action: Non-selective beta-adrenergic receptor antagonist.
Usage: Hypertension; angina; congestive heart failure; arrhythmia; essential tremor; migraine.
Toxicities: Bradycardia; bronchoconstriction; heart block; depression/sedation.
Other: Risk of MI and angina if abrupt cessation of treatment.
