Which medication is known to decrease the effectiveness of digoxin?

Cholestyramine is a bile acid sequestrant that can decrease the effectiveness of digoxin by binding to it in the gastrointestinal tract. When cholestyramine is administered, it can form an insoluble complex with digoxin, thereby reducing the absorption of the medication into the bloodstream. This leads to lower serum levels of digoxin, which may result in inadequate therapeutic effects for patients who rely on digoxin to manage heart failure or arrhythmias.

In contrast, medications like verapamil, amiodarone, and quinidine have different interactions with digoxin. Verapamil, a calcium channel blocker, can increase digoxin levels but does not reduce its effectiveness; it may instead increase the risk of digoxin toxicity. Amiodarone can also increase digoxin levels through various mechanisms, making monitoring essential but not affecting the medication's effectiveness negatively. Quinidine, on the other hand, can displace digoxin from tissue binding sites, potentially raising digoxin levels but not necessarily decreasing its effectiveness.

Understanding the interactions between these medications is crucial in managing heart failure and ensuring that digoxin provides its intended therapeutic benefits.