Antiarrhythmics Flashcards
(47 cards)
Class IA antiarrhythmic drugs
- Quinidine
- Procainamide
- Disopyramide
Class IA antiarrhythmic mechanism of action
- Block Na+ and K+ channels (phase 0 and phase 3)
- Intermediate dissociation rate (secs)
- Inc QRS and QT intervals
Class IB antiarrhythmic mechanism of action
- Block Na+ channels
- Rapid dissociation rate (<1 sec)
- Shortened QT interval
Class I antiarrhythmics block phase _
0
Class IC antiarrhythmic mechanism of action
- Block Na+ channels
- Slow dissociation rate (>10 sec)
- Inc QRS duration
Side effects with procainamide
- Rash, myalgia, vasculitis, Raynauds
- Fever, hypotension, bradycardia
- QT prolongation, Torsades de Pointes
- Drug induced lupus (oral)
Uses for procainamide
IV only
- Sustained vtach
- unmasking brugada syndrome
- AF in WPW
Class IB drugs
- lidocaine (IV)
2. mexiletine (oral)
Class ___ antiarrhythmics have increased potency in ischemic tissue
IB
Indications for class IB antiarrhythmics
- Vtach
- Vfib
* *not useful for atrial arrhythmias
Side effects of Class IB antiarrhythmics
Mainly CNS
lidocaine: visual disturbances, tremors, seizures, hallucinations, coma, asystole, hypotension, N/V
Mexiletine: GI: N/V/D, constipation, blurred vision, ataxia, HA, tremor, confusion
Class IC drugs
Flecainide
Propafenone
Indications for class IC antiarrhythmics
- Afib in patients without CAD or HF
2. SVT
Adverse effects of class IC antiarrhythmics
Flecainide: VT/VF in pts with CAD, aflutter, dizziness, dyspnea, HA, blurred vision, nausea, tremor, fatigue, HF exacerbation, AV block
Propafenone: unusual taste, dizziness, HA, nausea, fatigue, constipation, diarrhea, HF, blurred vision, bradycardia, palpitations, bronchospasms
Class II antiarrhythmic drugs
Beta blockers:
- Metoprolol
- Propranolol
- Esmolol
Mechanism of action of Class II antiarrhythmics
- Reduction in intracellular cAMP concentration
- Reduction of the funny current
- Slows and limits Ca++ influx
- Inc PR interval
- Dec slope of phase 4 depolarization
- Prolonged repolarization at AV node
Indications for class II antiarrhythmics
- Treat/prevent supraventricular and ventricular arrhythmias
- Afib/flutter: control ventricular rate
- Paroxysmal SVTs: terminate and prevent ventricular arrhythmias
- Ventricular arrhythmias: raise threshold for ventricular fibrillation in ischemic myocardium
- Reduce ventricular arrhythmias and cardiac arrest after ACS and in pts with HF
- Reduce DADs by reducing increases in Ca++ influx
Adverse effects of class II antiarrhythmics
- fatigue
- bronchospasm
- hypotension
- impotence
- depression
- HF exacerbation
- masking of symptoms of hypoglycemia in DM
Mechanism of action of class III antiarrhythmics
- Block K+ delayed rectifier current (phase 3)
- prolonged repolarization period
- prolonged QT interval
Class III antiarrhythmic drugs
- Dronedarone
- Amiodarone
- Sotalol
- Ibutilide
- Dofetilide
Mechanism of action of amiodarone
- K+ channel blocker (class III), prolongs action potential duration/phase 3
- Na+ channel blocker (class I), blocks inactivated Na+ channels, relatively rapid rate of recovery
- L-type Ca++ blocker (class IV), slows sinus and AV node conduction
- B1, B2, a1 receptor blocker (class II), slows sinus and AV node conduction
True/false: amiodarone works best at high HRs
True
Pharmacokinetics of amiodarone
- Highly lipophilic (large volume of distribution)
- Delayed onset of action (need loading dose 10g total)
- T1/2 of 2months
- Hepatic metabolism CYP3A4 and 2C8 to active metabolite
- Inhibits CYP3A4, CYP2C9 and P-glycoprotein (drug interactions with digoxin, warfarin, statins)
Contraindications for amiodarone
- known hypersensitivity to amiodarone, including iodine
- Cardiogenic shock
- marked sinus bradycardia
- 2nd or 3rd degree AV block w/out pacemaker
