Influence of assay methodologies and interferences on the interpretation of digoxin concentrations.

The interpretation of serum digoxin concentrations is an area where pharmacists can have substantial clinical input. Important in this interpretation is the knowledge of various factors that may interfere with the reported concentration. These include drugs, metabolites of digoxin, protein concentration, and endogenous digoxin-like substances. The patients for whom these interferences are most significant include neonates, patients with renal failure and liver disease, and pregnant women. Pharmacist knowledge of these interferences can have an important impact on the quality of patient care.