Triamterene is a potassium-sparing diuretic that may protect against diuretic-induced digoxin toxicity. Digoxin toxicity may be caused by drugs that increase serum digoxin levels or increase the binding of digoxin to its receptor, the sodium-potassium adenosine tn phosphatase (ATPase). Quinidine decreases digoxin volume of distribution and clearance. Verapamil also decreases the clearance of digoxin. Both drugs may thereby increase serum digoxin levels and precipitate digoxin toxicity. Diuretics (e.g., hydrochlorothiazide, furosemide) may cause hypokalemia and hypomagnesemia, both of which may predispose to cardiac arrhythmias. Furthermore, hypokalemia increases di-goxin binding to sodium-potassium ATPase.