**Core Concept**
The maintenance dose of digoxin is a crucial aspect of its pharmacological management, as it requires careful consideration of the patient's renal function, age, and body weight to prevent toxicity. Digoxin is a cardiac glycoside that inhibits the sodium-potassium ATPase pump, leading to an increase in intracellular calcium and a subsequent positive inotropic effect.

**Why the Correct Answer is Right**
The maintenance dose of digoxin is typically 0.125-0.25 mg/day, and it is recommended to adjust the dose based on the patient's serum digoxin levels and clinical response. The dose should be reduced in patients with renal impairment, as digoxin is primarily excreted through the kidneys. The correct formula for calculating the maintenance dose of digoxin is:

Maintenance dose = (Total body clearance x Desired steady-state concentration) / 24 hours

In patients with normal renal function, the total body clearance of digoxin is approximately 28 mL/min. The desired steady-state concentration of digoxin is typically 0.5-1.5 ng/mL.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not take into account the patient's renal function and age. Digoxin toxicity is more common in patients with renal impairment, and the dose should be adjusted accordingly.
**Option B:** This option is incorrect because it is too high and may lead to digoxin toxicity. The maximum recommended dose of digoxin is 0.5 mg/day.
**Option C:** This option is incorrect because it does not specify a dose adjustment for patients with renal impairment.

**Clinical Pearl / High-Yield Fact**
To remember the correct maintenance dose of digoxin, use the mnemonic "START" - Set the dose based on the patient's renal function, Age, Total body clearance, and Renal impairment. This will help you to calculate the correct dose and prevent digoxin toxicity.

**Correct Answer:** C. 0.125-0.25 mg/day