Digoxin immune Fab dosing is determined by what factors?

• A. Amount ingested and serum digoxin level
• B. Time since ingestion
• C. Patient weight only
• D. Degree of symptoms only

Answer: (A)

The key idea here is that Digoxin immune Fab dosing is driven by neutralizing the total body burden of digoxin. The amount of Fab you give should reflect how much digoxin is present and able to cause toxicity. Practically, you estimate this burden in two main ways: if the patient or history provides a known ingestion amount, you calculate how many vials are needed based on that load (each vial binds a fixed amount of digoxin). If the ingestion amount isn’t known, the serum digoxin concentration at presentation serves as a proxy for the body burden, guiding how many vials to administer. Time since ingestion and the patient’s symptoms influence monitoring and whether additional doses may be required later due to redistribution, but they don’t determine the initial Fab dose as directly as the estimated digoxin load. Weight isn’t a primary determinant; the critical factors are how much digoxin was taken and what the current serum level is.