The maximum digoxin dose is given by which route?

• A. IV
• B. Subcutaneous
• C. Oral
• D. IM

Answer: (C)

The amount of digoxin that reaches the bloodstream (bioavailability) depends on the route. Intravenous administration delivers the entire dose directly into the circulation, giving 100% bioavailability and thus the highest possible systemic exposure. Oral digoxin, by contrast, has incomplete and variable absorption—roughly 60–80% on average and influenced by factors like food and individual GI differences—so the same nominal dose results in lower and less predictable plasma levels. Subcutaneous and intramuscular routes are not standard for digoxin because absorption from these sites can be unreliable and slower, making it hard to achieve a maximum or consistent dose. Therefore, the route that allows the greatest potential dose to reach the systemic circulation is intravenous. In practice, oral dosing is used for maintenance with careful monitoring due to the drug’s narrow therapeutic index.