Disopyramide

• Overview:
  • Very similar to quinidine gluconate (Quinaglute, Quinalan)
  • Greater antimuscarinic effects (in management of atrial flutter & fibrillation, pre-treatment with a drug that reduces AV conduction velocity is required)
  • Approved use (USA): ventricular arrhythmias
• Metabolism:
  • Dealkylated metabolite (hepatic); less anticholinergic, less antiarrhythmic effect compared apparent compound
  • 50% -- excreted unchanged, renal
• Electrophysiological effects similar to quinidine gluconate (Quinaglute, Quinalan)
  • Similar to quinidine gluconate (Quinaglute, Quinalan) in effective ventricular and atrial tachyarrhythmia suppression
  • prescribed to maintain normal sinus rhythm in patients prone to atrial fibrillation and flutter and is also used to prevent ventricular fibrillation or tachycardia.
• Side Effects/Toxicity
  • Adverse side-effect profile: different from qunidine's in that disopyramide (Norpace) is not an alpha-adrenergic receptor blocker but is anti-vagal.
  • Most common side effects: (anticholinergic)
    • dry mouth
    • urinary hesitancy
  • Other side effects: blurred vision, nausea
  • Cardiovascular:
    • QT interval prolongation (ECG)
    • paradoxical ventricular tachycardia (quinidine-like)
  • Negative inotropism (significant myocardial depressive effects)--undesirable with preexisting left ventricular dysfunction (may promote congestive heart failure, even in patients with no prior evidence of myocardial dysfunction)
    • Disopyramide is not a first-line antiarrhythmic agent because of its negative inotropic effects
    • If used, great caution must be exercised in patients with congestive heart failure
  • Can cause torsades de pointes, a ventricular arrhythmia

Hondeghem, L.M. and Roden, D.M., "Agents Used in Cardiac Arrhythmias", in Basic and Clinical Pharmacology, Katzung, B.G., editor, Appleton & Lange, 1998, pp 216-241;Stoelting, R.K., "Cardiac Antidysrhythmic Drugs", in Pharmacology and Physiology in Anesthetic Practice, Lippincott-Raven Publishers, 1999, 331-343

Category: Pharmacology Notes