III. ANTIARRHTHYMIC DRUGS: ADVERSE REACTIONS AND DRUG INTERACTIONS Contraindications and W

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III. ANTIARRHTHYMIC DRUGS: ADVERSE REACTIONS AND DRUG INTERACTIONS Contraindications and Warnings * Sick sinus syndrome, AV conduction defect: all antiarrhythmic agents should be used with caution. Complete AV block is an absolute contraindication to the use of any antiarrhythmic unless a ventricular pacemaker is in place. * Congestive heart failure: Beta blockers, verapamil, disopyramide, flecainide * Pulmonary disease: Amiodarone * Liver disease: Amiodarone * Hematologic disease: Quinidine, procainamide Toxicity of antiarrhythmic drugs: * Amiodarone: Resp: pulmonary alveolitis and fibrosis. CV: Arrhythmia exacerbation, bradycardia, arrest Endocrine: Hyper- or hypothyroidism Eye: Microcrystalline corneal deposits Liver:Elevated enzymes, liver failure (PgDn key for more text) * Beta blockers (acebutolol and propranolol): CV: Sinus arrest, AV block, congestive failure, Resp: Bronchoconstriction * Bretylium: CV: Exacerbation of arrhythmias, orthostatic hypotension, bradycardia GI: Nausea, vomiting * Digoxin: CV: PVCs, AV block, ventricular tachycardia or fibrillation GI: Nausea, vomiting, diarrhea, anorexia * Disopyramide ANS:Marked muscarinic block, potential for glaucoma, urinary retention CV: Depressed cardiac output * Flecainide CV: New or exacerbated arrhythmia, decreased cardiac output and hypotension, conduction block, sinus bradycardia or tachycardia CNS:Dizziness, syncope, paresthesias, headache, fatigue, confusion, GI: Nausea, vomiting, anorexia (PgDn key for more text) * Lidocaine CNS:Drowsiness, dizziness, seizures CV: Hypotension * Mexiletine CNS:Dizziness,headaches,tinnitus, CV: Palpitations, angina, hypotension GI: Nausea, vomiting, constipation * Phenytoin CNS:Ataxia, nystagmus, confusion * Procainamide Immunologic: Positive antinuclear antibody test develops in 60-70% of patients, and a (usually) reversible lupus-like state appears in 15-20% of those treated for 1-12 months. Angioneurotic edema has been reported. CV: Hypotension with parenteral administration Hematologic: Agranulocytosis, thrombocytopenia Overdosage: Lethargy, confusion, hypotension, cardiac conduction defects with bizarre QRS complexes, nausea and vomiting. (PgDn key for more text) * Quinidine CNS: Headache, tinnitus, vertigo, visual disturbance (cinchonism) GI: Nausea, vomiting, diarrhea CV: Widening of the QT complex associated with syncope - probably the result of brief episodes of polymorphous ventricular tachycardia (torsade de pointes) Hematologic: Thrombocytopenia, agranulocytosis Overdosage: Lethargy, coma, cardiac conduction defects, hypotension, ventricular fibrillation * Tocainide CNS:Dizziness, syncope, tremor, confusion, hallucinations, coma GI: Nausea, vomiting, anorexia, diarrhea CV: Hypotension, bradycardia, PVCs * Verapamil CV: Hypotension, bradycardia or sinus arrest, AV blockade, congestive heart failure, peripheral edema GI: Constipation CNS: headache (PgDn key for more text) Drug Interactions * Cardiac: verapamil and beta-blockers have additive depressant effects on nodal function. Group IA plus IB, or group IA plus beta-blockers may have beneficial additive effects on arrhythmias. * Pharmacokinetic: Increase the serum level of digoxin: quinidine, verapamil, amiodarone * Autonomic: Additive muscarinic block: disopyramide * Neuromuscular: Increase block by curariform drugs: procainamide, quinidine, * Hematologic: Increase effect of warfarin: amiodarone, (Home key to return to top of file)

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