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. Concomitant use of digoxin and sympathomimetics increases the risk of cardiac arrhythmias. Succinylcholine may cause a sudden extrusion of potas-sium from muscle cells, and may thereby cause arrhythmias in digital-ized patients. Although beta-adrenergic blockers or calcium channel blockers and digoxin may be useful in combination to control atrial fib-rillation, their additive effects on AV node conduction can result in advanced or complete heart block. Due to the considerable variability of these interactions, the dosage of digoxin should be individualized when patients receive these medications concurrently. Furthermore, caution should be exercised when combining digoxin with any drug that may cause a significant deterioration in renal function, since a decline in glomerular filtration or tubular secretion may impair the excretion of digoxin. | ||||
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