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26 terms

Cardiac Drugs

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Class I
Sodium channel blockers
Class Ia
increase duration of action potential by slowing phase 0
Class Ib
decrease duration of action potential by shortening phase 3
Class Ic
minimal change in action potential duration; increases threshold potential, thus slowing conduction velocity
Class II
Beta-adrenergic blockers; diminish phase 4, thus depressing automaticity and decreasing heart rate; effective at preventing arrhythmias after an MI; both supraventricular and ventricular tachyarrhythmias respond well
Class III
Potassium channel blockers; extend phase 3
Class IV
Calcium channel blockers; slow SA and AV nodal conduction; decrease rate of phase 4 and thus increase the effective refractory period
Quinidine
Class Ia; for VTach and Supraventricular arrhythmias; Prolongs QT
Procainamide
Class Ia; for ventricular and supraventricular arrhythmias; metabolite has some class III action; LUPUS-like syndrome
Disopyramide
Class Ia; for ventricular and supraventricular arrhythmias; causes prostatism and anticholinergic effects
Lidocaine
Class Ib; can be used for acute management of ventricular arrhythmias in patients with myocardial infarction, but amiodarone is better; also local anesthetic; nystagmus is early sign of toxicity
Tocainide
Class Ib; for ventricular arrhythmias; can cause pulmonary fibrosis or bone marrow aplasia
Mexiletine
Class Ib; for ventricular arrhythmias; blood dyscrasias, nystagmus, leukopenia, agranulocytosis
Phenytoin
Class Ib; D.O.C. for treating digoxin-induced atrial and ventricular arrhythmias; anticonvulsant; gingival hyperplasia, serious bone marrow and derm reactions can occur
Flecainide
Class Ic; for treating life-threatening ventricular arrhythmias in patients without myocardial structural abnormalities; used as last-line b/c it can cause arrhythmias; heart block is possible toxicity; blocks Na+ in purkinje shortening AP while blocking K+ in ventricles extending AP-->no change in AP duration
Propafenone
Class Ic; for treating supraventricular and ventricular arrhythmias; similar action as flecainide but also beta blocker activity; hepatic metabolism
Moricizine
Class Ic; for severe ventricular arrhythmias
Esmolol
Class II; very short acting beta blocker; almost always used in treatment of acute surgical arrhythmias
Sotalol
Class III; treats ventricular tachyarrhythmias and supraventricular arrhythmias
Bretylium
Class III; prolongs ventricular action potential and effective refractory period; also blocks norepinephrine release; used to treat refractory VFib and VTach during cardiac arrest; rarely used
Amiodarone
Class III; class I-IV activity, but mostly III; adverse effects=pulmonary fibrosis, hepatocellular necrosis, CNS (tremor, ataxia), Photosensitivity, corneal microdeposits, thyroid dysfunction, blue skin discoloration; CHECK PFTs, LFTs, and TFTs
Ibutilide
Class III; for atrial flutter and fibrillation; toxicity=torsades de pointes
Dofetilide
Class III; used to maintain sinus rhythm in patients w/ atrial fibrillation or flutter; toxicity=torsades de pointes
Digoxin
Inhibits Na/K-ATPase; increases refractory period and decreases conduction time of AV node; for treating supraventricular arrhythmias and CHF; toxicity=atrial of ventricular dysrhythmias (ATach, often); treat toxicity w/ digoxin antibodies.....or phenytoin!!
Magnesium Sulfate
Stabilizes cardiac cell membranes; for treating torsades de pointes
Adenosine
Activates ACh-sensitive K+ channels-->shortened AP duration, hyperpolarization, and decreased automaticity; for diagnosing and terminating paroxysmal supraventricular tachyarrhythmias because of its limited toxicities and rapid onset