Anti-arrhythmic drugs: uses, adult doses and adverse effects
THE CONTEXT
The table compares class I–IV anti-arrhythmic drugs by indication, route, adult dosage and important adverse effects.
Class I drugs
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Disopyramide prevents and treats atrial and ventricular tachyarrhythmias. Its intravenous regimen is 2 mg/kg at 30 mg/min, followed by 0.4 mg/kg/hr, with a maximum of 800 mg/day. Adverse effects include myocardial depression, hypotension, dry mouth and urinary retention.
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Lidocaine treats and provides short-term prevention of ventricular tachycardia and ventricular fibrillation. The intravenous regimen is a 50–100 mg bolus, then 4 mg/min for 30 minutes, 2 mg/min for 2 hours and 1 mg/min for 24 hours. Important adverse effects are myocardial depression, delirium and convulsions.
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Mexiletine prevents and treats ventricular tachyarrhythmias. Intravenous loading comprises 100–250 mg at 25 mg/min, followed by 250 mg in 1 hour and 250 mg in 2 hours; maintenance is 0.5 mg/min. The listed oral dose is 167–500 mg daily. Adverse effects include myocardial depression, gastrointestinal irritation, delirium, dizziness, tremor, nystagmus and ataxia.
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Flecainide prevents and treats atrial and ventricular tachyarrhythmias. Intravenous dosing is 2 mg/kg over 10 minutes, followed if required by 1.5 mg/kg/hr for 1 hour and then 0.1 mg/kg/hr. Oral dosing is 50–150 mg twice daily. Myocardial depression and dizziness are important adverse effects.
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Propafenone prevents and treats atrial and ventricular tachyarrhythmias. Oral dosing is 150 mg three times daily for 1 week, then 300 mg twice daily. Important adverse effects are myocardial depression and dizziness.
Class II drugs
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Atenolol treats and prevents supraventricular tachycardia and atrial fibrillation, and prevents ventricular ectopics and exercise-induced ventricular fibrillation. Intravenous dosing is 2.5 mg at 1 mg/min, repeated at 5-minute intervals to a maximum of 10 mg; oral dosing is 25–100 mg daily.
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The adverse-effect entry accompanying atenolol lists myocardial depression, bradycardia, bronchospasm, fatigue, depression, nightmares and cold peripheries.
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Bisoprolol is listed at 2.5–10 mg orally daily. Metoprolol is listed at 5 mg intravenously over 2 minutes, to a maximum of 15 mg.
Class III drugs
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Amiodarone is used for serious or resistant atrial and ventricular tachyarrhythmias. Intravenous dosing is 5 mg/kg over 20–120 minutes, then up to 15 mg/kg over 24 hours. Oral dosing is initially 600–1200 mg/day, then 100–400 mg daily.
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Amiodarone adverse effects include photosensitivity, skin discoloration, corneal deposits, thyroid dysfunction, alveolitis, nausea and vomiting, hepatotoxicity, peripheral neuropathy and torsades de pointes. It potentiates digoxin and warfarin.
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Dronedarone is listed for paroxysmal atrial fibrillation at 400 mg orally twice daily. Renal and hepatic dysfunction require regular blood monitoring.
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Sotalol is listed for atrial fibrillation and, rarely, ventricular tachyarrhythmias. Doses are 10–20 mg intravenously slowly or 40–160 mg orally twice daily. It can cause torsades de pointes.
Class IV: verapamil
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Verapamil treats supraventricular tachycardia and controls atrial fibrillation. Doses are 5–10 mg intravenously over 30 seconds, 40–120 mg orally three times daily, or 240 mg sustained-release daily.
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Important adverse effects of verapamil are myocardial depression, hypotension, bradycardia and constipation.