**Core Concept**
Digoxin is a cardiac glycoside used in the treatment of heart failure and atrial fibrillation. Its pharmacokinetics is characterized by a relatively long half-life, which is crucial for determining its dosing and potential toxicity.

**Why the Correct Answer is Right**
The half-life of digoxin is approximately 40 hours, which is a result of its slow elimination from the body. Digoxin is primarily eliminated by the kidneys, but it also undergoes enterohepatic recirculation, which prolongs its half-life. The half-life of digoxin is also affected by factors such as age, renal function, and electrolyte imbalances. In patients with impaired renal function, the half-life of digoxin can be significantly prolonged, increasing the risk of toxicity.

**Why Each Wrong Option is Incorrect**
**Option A:** 24 hours is too short for the half-life of digoxin, as it would require more frequent dosing and increase the risk of toxicity.
**Option C:** 48 hours is still shorter than the actual half-life of digoxin, and would not accurately reflect its pharmacokinetics.
**Option D:** 60 hours is longer than the actual half-life of digoxin, but it is not the closest estimate.

**Clinical Pearl / High-Yield Fact**
The half-life of digoxin is a critical factor in its dosing and monitoring. In patients with renal impairment, the half-life of digoxin can be prolonged, and close monitoring of serum digoxin levels is essential to prevent toxicity.

**✓ Correct Answer: B. 40 hours**