Flecainide Digoxin

As with other Class I agents, patients treated with flecainide for atrial flutter have been reported with 1 1 atrioventricular conduction due to slowing the atrial rate. A paradoxical increase in the ventricular rate also may occur in patients with atrial fibrillation who receive flecainide. Concomitant negative chronotropic therapy such as digoxin or beta-blockers may lower the risk of this complication. 

Drugs that may affect flecainide include amiodarone, cimetidine, cisapride, disopyramide, propranolol, ritonavir, urinary acidifiers/alkalinizers, and verapamil. Smoking may also have an effect. Drugs that may be affected by flecainide include cisapride, propranolol, and digoxin. 

Drugs that may affect amiodarone include hydantoins, cholestyramine, fluoroquinolones, rifamycins, ritonavir, and cimetidine. Drugs that may be affected by amiodarone include anticoagulants, beta-blockers, calcium channel blockers, cyclosporine, dextromethorphan, digoxin, disopyramide, fentanyl, flecainide, hydantoins, lidocaine, methotrexate, procainamide, quinidine, and theophylline. Drug/Lab test interactions Amiodarone alters the results of thyroid function tests, causing an increase in serum T4 and serum reverse T3 levels and a decline in... 

Drugs that may be affected by antacids include allopurinol, amphetamines, benzodiazepines, captopril, chloroquine, corticosteroids, dicumarol, diflunisal, digoxin, ethambutol, flecainide, fluoroquinolones, histamine H2 antagonists,... 

In patients whose condition has been stabilized by flecainide, the addition of cimetidine may reduce the rate of flecainide s hepatic metabolism, increasing the potential for toxicity. Flecainide may increase digoxin concentrations on concurrent administration. 

Amiodarone increases the hypoprothrombinemic response to warfarin (an oral anticoagulant) by reducing its metabolism. Patients receiving digoxin may undergo an increase in serum digoxin concentrations when amiodarone is added to the treatment regimen. Amiodarone interferes with hepatic and renal elimination of flecainide, phenytoin, and quinidine. 

Drug Interactions Other antihypertensive agents Carbamazepine (vasodilators, ACE inhibitors, Rifampin diuretics, and beta-blockers) Phenobarbital Digoxin Cyclosporine Disopyramide Theophylline Flecainide Inhalation anesthetics Quinidine Neuromuscular blocking agents Cimetidine Lithium ... 

Of 26 fetuses with hydrops fetalis and supraventricular tachycardias, 25 received transplacental drug therapy prenatal conversion occurred in 15 (82). Nine fetuses were converted to sinus rhythm using either flecainide (n = 7) or amiodarone (n = 2) as first-line therapy, while digoxin either alone or in association with sotalol failed to restore sinus rhythm in all cases. After first-line therapy, supraventricular tachycardia persisted in 10 fetuses, nine of whom received amiodarone alone or in association with digoxin as second-line therapy, and five of whom converted to sinus rhythm. Of 11 neonates who received amiodarone in utero, two developed raised thyroid stimulating hormone concentrations on postnatal days 3-4 they received thyroid hormone and had normal outcomes. 

This occurs in otherwise healthy individuals, who possess an anomalous (accessory) atrioventricular pathway they often experience attacks of paroxj mal AV re-entrant tachycardia or atrial fibrillation. Drugs that both suppress the initiating ectopic beats and delay conduction through the accessory pathway are used to prevent attacks e.g. flecainide, sotalol or amiodarone. Verapamil and digoxin may increase conduction through the anomalous pathway and should not be used. Electrical conversion may be needed to restore sinus rhythm when the ventricular rate is very rapid. Radiofrequency ablation of aberrant pathways will almost certainly provide a cure. 

Adenosine does not interact with digoxin, disopyramide, flecainide, or quinidine. 

Lewis GP, Holtzman JL. Interaction of flecainide with digoxin and propranolol. Am J Cardiol 1984 53(5) B52-7. 

Despite an early report that flecainide might alter the pharmacokinetics of digoxin, this action is minimal and probably of no clinical significance (72). The combination canses a significant increase in the PR interval but the clinical significance of this is unclear, it may be important for patients with impaired sinus node function (73). 

Prolong PR, QRS and QT. PO/IV. Maximal response may take weeks. Serum levels correspond poorly w/efficacy. Increases serum levels of digoxin, warfarin, flecainide. ... 

Diuretics. Hypercalcaemia may develop in patients administered thiazide diuretics with either calcium or vitamin D supplements, leading to a need to monitor plasma or serum calcium levels. The concurrent use of potassium-sparing diuretics, and other potassium supplements or potassium-containing salt substitutes, could lead to serious hyperkalaemia. Hyperkalaemia is known to interfere with the absorption of vitamin B12. There is a need to warn patients and monitor serum potassium levels. The risk of hypokalaemia is minimal with low doses of thiazides, for example 5 mg of bendroflumethiazide. Hypokalaemia is a concern in patients receiving treatment with drugs such as digoxin, amiodarone, disopyramide or flecainide (drugs used to treat cardiac disorders). 

Another report describes atrioventricular block in a patient with a pacemaker when treated with digoxin, flecainide and verapamil. ... 

Plasma digoxin levels are unaltered or only modestly increased by the use of flecainide, but this is not likely to be important in most patients. 

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