A 66-Year-Old Man Is Admitted to the Hospital with Confusion

A 66-year-old man is admitted to the hospital with confusion, nausea, and blurred vision. He is currently on digoxin for the treatment of heart failure. On physical exam, his heart rate is 120 bpm. Further evaluation reveals a digoxin level of 5.3 ng/mL (normal range: 0.5-2 ng/mL) . The doctor believes his symptoms are due to digoxin toxicity. Which parameter is used to indicate the ability of digoxin to produce the desired effect relative to a toxic effect?

A) Bioavailability
B) Efficacy
C) Intrinsic activity
D) Potency
E) Therapeutic index