**Core Concept:** Digital toxicity from digoxin is a consequence of elevated digoxin levels in the blood, leading to adverse effects on the heart and other organs. In this scenario, we are trying to determine the duration of digoxin suspension to reach a safer therapeutic level.

**Why the Correct Answer is Right:**
Digital toxicity occurs when the plasma digoxin concentration exceeds its therapeutic range of 0.5-2 ng/ml. In this case, the patient's current digoxin level is 4 ng/ml, which is well above the therapeutic range. The half-life of digoxin is 1.6 days, which means that digoxin levels will decrease by half every 1.6 days. To reach a safe and therapeutic level of 1 ng/ml, we need to calculate the time required for digoxin levels to decrease by half.

**Why Each Wrong Option is Incorrect:**
A) The patient is not experiencing renal failure, so renal clearance does not play a significant role in digoxin elimination.
B) Renal function has not been mentioned as being impaired, so we do not need to consider changes in digoxin clearance due to renal dysfunction.
C) The patient's renal function is normal, so we do not need to adjust the digoxin dosage based on renal function.
D) Digoxin elimination is primarily determined by its half-life (1.6 days), not the patient's age.

**Clinical Pearl:**
To determine the digoxin dosage adjustment required, we should focus on the half-life (1.6 days) rather than the patient's age.

**Correct Answer:**
To decrease the plasma digoxin level from 4 ng/ml to 1 ng/ml, it would take 3.2 days (1.6*2). Thus, digoxin therapy should be withheld for 3.2 days. After this period, the patient's digoxin level should decrease by half, reaching a safe therapeutic range of 1 ng/ml.