observed a mean increase in plasma digoxin concentration of 70% in seven patients when amoidarone, 600 mg/day, was administered concurrently with digoxin. a daily amiodarone dose of 400 mg is sufficient to reduce clearance of a digoxin concentration by 26%
Other antiarrhythmic drugs: There are several antiarrhythmic drugs that do not appear to have any clinically relevant pharmacokinetic interactions with digoxin. These include procainamide , disopyramide mexiletine, flecainide and ethmozine.
– Interaction of Digoxin With Calcium Channel
Blocking Drugs Interaction of Digoxin With Calcium Channel Blocking Drugs The pharmacokinetic interaction between digoxin and calcium channel blocking drugs varies from none with nifedipine to an increased serum digoxin level of more than 70% when verapamil and digoxin are given concomitantly.
Verapamil : They found that the effect of verapamil on serum digoxin concentration developed gradually within the first few days after verapamil was co-administered with digoxin and approached the new steady state value within 7 days after the start of verapamil therapy. When the serum digoxin levels are markedly elevated as a result of administration of verapamil, lethal cardiac toxicity may occur . The elevated plasma digoxin concentration induced by verapamil is associated with an inotropic effect as assessed by a measurement of systolic time intervals . The mechanism of the digoxin-verapamil interaction consists of decreases in both renal and extra renal clearance of digoxin by verapamil . Since the creatinine clearance does not change under the influence of verapamil , the decreased renal clearance of digoxin appears to be due to an inhibition of tubular secretion. reported that serum digoxin levels increased 70% during concurrent treatment with verapamil .
Diltiazem,: An average increase in steady state plasma digoxin concentration of 22% was observed when diltiazem, 180 mg/day, was given to 24 normal subjects who were receiving l3-acetyldigoxin, 0.2 mg daily . There is minimal pharmacokinetic interaction between diltiazem and digoxin . The magnitude of the diltiazem interaction is small; therefore, digoxin dose adjustment is probably unnecessary
Nifedipine : There is no pharmacokinetic interaction between nifedipine and digoxin, either in patients or in normal subjects .
Tiapamil, a congener of verapamil, causes an increase in serum digoxin levels of 60%, similar to that of verapamil .
