potential duration and dissociates from INa channel with intermediate arrhythmias • drug of second choice for most sustained ventricular arrhythmias associated with acute myocardial infarction
Oral, IV, IM • eliminated by hepatic metabolism to N-acetylprocainamide (NAPA; see text) and renal elimination • NAPA implicated in torsades de pointes in patients with renal failure • Toxicity: Hypotension • long-term therapy
Quinidine: Similar to procainamide but more toxic (cinchonism, torsades); rarely used in arrhythmias; see Chapter 52 for malaria
Mexiletine: Orally active congener of lidocaine; used in ventricular arrhythmias, chronic pain syndromes
Propafenone: Orally active, weak β-blocking activity; supraventricular arrhythmias; hepatic metabolism
Moricizine: Phenothiazine derivative, orally active; ventricular arrhythmias, proarrhythmic. Withdrawn in USA.
• Esmolol: Short-acting, IV only; used for intraoperative and other acute arrhythmias
Atrial arrhythmias and prevention of recurrent infarction and sudden death
Oral, parenteral • duration 4–6 h • Toxicity: Asthma, AV blockade, acute heart failure • Interactions: With other cardiac depressants and hypotensive drugs
CLASS 3 •AmiodaroneBlocks IKr, INa, ICa-L channels, βadrenoceptors Prolongs action potential duration andQTinterval•slowsheartrateandAVnodeconduction•lowincidence of torsades de pointes Serious ventricular arrhythmias and supraventricular arrhythmias Oral,IV•variableabsorptionandtissueaccumulation•hepaticmetabolism,eliminationcomplexandslow•Toxicity: Bradycardia and heart block in diseased heart, peripheral vasodilation, pulmonaryandhepatictoxicity•hyper-orhypothyroidism.•Interactions: Many, based on CYP metabolism •DofetilideIKr block Prolongs action potential, effective refractory period Maintenance or restoration of sinus rhythm in atrial fibrillation Oral•renalexcretion•Toxicity: Torsades de pointes (initiate in hospital with monitoring)•Interactions: Additive with other QT-prolonging drugs
Sotalol: β-Adrenergic and IKr blocker, direct action potential prolongation properties, use for ventricular arrhythmias, atrial fibrillation
Ibutilide: Potassium channel blocker, may activate inward current; IV use for conversion in atrial flutter and fibrillation
Dronedarone: Amiodarone derivative; multichannel actions, reduces mortality in patients with atrial fibrillation
Vernakalant: Investigational in the USA, multichannel actions in atria, prolongs atrial refractoriness, effective in atrial fibrillation