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


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     * 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

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     * 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.


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     * 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


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     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,











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