All are true about Digoxin except
**Core Concept**
Digoxin is a cardiac glycoside used in the management of heart failure and atrial fibrillation. It works by inhibiting the sodium-potassium ATPase pump, leading to an increase in intracellular calcium levels and a subsequent increase in contractility.
**Why the Correct Answer is Right**
Digoxin increases contractility by increasing the sensitivity of the myocardium to calcium ions. This is achieved through the inhibition of the sodium-potassium ATPase pump, which results in an increase in intracellular sodium levels. The increased sodium levels lead to an increase in intracellular calcium levels through the sodium-calcium exchange mechanism. The increased calcium levels then increase the contractility of the myocardium. Digoxin also has a vagolytic effect, which helps to control the ventricular rate in patients with atrial fibrillation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a true statement about digoxin. Digoxin does indeed increase contractility and is used in the management of heart failure.
**Option B:** This option is incorrect because it is a true statement about digoxin. Digoxin does indeed have a vagolytic effect, which helps to control the ventricular rate in patients with atrial fibrillation.
**Option C:** This option is incorrect because it is a true statement about digoxin. Digoxin is indeed used in the management of atrial fibrillation.
**Clinical Pearl / High-Yield Fact**
One of the major side effects of digoxin is its narrow therapeutic index, which means that the difference between a therapeutic dose and a toxic dose is small. This can lead to toxicity, which is often manifested as nausea, vomiting, and arrhythmias.
**Correct Answer:** D