Flecainide with digoxin

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

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. 

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

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

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. 

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. 

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). 

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). 

The plasma digoxin levels of 10 patients with congestive heart failure were unchanged when they took flecainide 100 to 200 mg twice daily for 7 days. A similar lack of interaction was also seen in 4 patients who took both drugs over a 4-week period. ... 

McQuinn RL, Kvam DC, Parrish L, Fox TL, Miller AM, Franciosa lA. Digoxin levels in patients with ca estive h rt failure are not altered by flecainide. ClinPhatmacol Ther 9ZZ) 43,150. 

---