A 55-year-old man with chronic cardiac failure currently takes multiple medications, including digoxin. He is brought to the emergency department because of slurred speech and inappropriate behavior. It turns out that he has not taken his digoxin for the last 2 weeks. The physician gives 125 mg as standard dose. Twenty-four hours later, his serum levels were reported to be 2 ng/mL (2 mg/L). The target therapeutic level is 0.8 ng/mL. What dose of digoxin should he receive? (A) 25 mg (B) 50 mg (C) 75 mg (D) 100 mg (E) 125 mg