What is the maximum oral dose of digoxin?

• A. 0.25 mg
• B. 5 mg
• C. 1-2.5 mg
• D. 10 mg

Answer: (C)

Digoxin has a very narrow therapeutic window, so the total amount given by mouth each day is kept very small. The safety margin is tight, meaning small increases in dose can push levels into toxicity, which can cause dangerous heart rhythms and other symptoms. Because of this, the maximum oral daily dose is limited to a small total amount, in the low single-digit milligram range. Lower doses are generally enough for effect when used properly, while higher ones risk toxicity. The other options are either far too small to achieve the desired effect or far too high for safe oral use, so the moderate total daily oral dose within that small range is the best fit.