What is the therapeutic serum level range for digoxin?

• A. 0.1-0.5
• B. 2.5-3.5
• C. 0.5-2.0
• D. 1-2.5

Answer: (C)

Digoxin works best when its blood level sits in a narrow window: high enough to provide clinical benefit but not so high that toxicity occurs. The therapeutic serum concentration is about 0.5 to 2.0 ng/mL. Levels below this range may not adequately improve symptoms of heart failure or rate control in atrial fibrillation, while levels above this range, especially approaching or exceeding 2.5 ng/mL, raise the risk of serious toxicity such as arrhythmias, gastrointestinal symptoms, and CNS signs. Because digoxin is cleared largely by the kidneys and interacts with other drugs, clinicians monitor trough levels after starting or adjusting therapy and tailor the target range to the patient’s kidney function and clinical situation.