Digitek

[digoxin]

Sinus bradycardia may be a sign of impending digoxin intoxication, especially in infants, even in the absence of first-degree heart block. Any arrhythmia or alteration in cardiac conduction that develops in a child taking digoxin should be assumed to be caused by digoxin, until further evaluation proves otherwise.

Drug Interactions

Potassium-depleting diuretics are a major con-tributing factor to digitalis toxicity. Calcium, particularly if adminis-tered rapidly by the intravenous route, may produce serious arrhyth-mias in digitalized patients. Quinidine, verapamil, amiodarone, propafenone, indomethacin, itraconazole, alprazolam, and spirono-lactone raise the serum digoxin concentration due to a reduction in clearance and/ or in volume of distribution of the drug, with the impli-cation that digitalis intoxication may result. Erythromycin and clarithromycin (and possibly other macrolide antibiotics) and tetracycline may increase digoxin absorption in patients who inactivate digoxin by bacterial metabolism in the lower intestine, so that digitalis intoxication may result (see CLINICAL PHARMACOLOGY: Absorption).

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Propantheline and diphenoxylate, by decreasing gut motility, may increase digoxin absorption. Antacids, kaolin-pectin, sulfasalazine, neomycin, choles-tyramine, certain anticancer drugs, and metoclopramide may interfere with intestinal digoxin absorption, resulting in unexpectedly low serum concentrations.

Rifampin may decrease serum digoxin concentration, especially in patients with renal dysfunction, by increasing the non-renal clearance of digoxin. There have been inconsistent reports regard-ing the effects of other drugs [e. g., quinine, penicillamine] on serum digoxin concentration. Thyroid administration to a digitalized, hypothy-roid patient may increase the dose requirement of digoxin.

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