Digoxin: Review of Current Laboratory Practice and Considerations

Digoxin is a drug used for its effects on the heart, particularly its effect on rate and strength of contraction. Levels are particularly useful in clinical practice owing to its narrow therapeutic index, with toxicity and therapeutic levels being relatively close. Clinically, digoxin toxicity can be acute or chronic, and can manifest with signs and symptoms related to the gastrointestinal system, nervous system, and cardiovascular system. Given digoxin toxicity can lead to fatal dysrhythmias, accurate and reproducible analysis by the laboratory is essential in the treatment of patients with suspected digoxin toxicity. However, the laboratory workup for digoxin toxicity is not as simple as performing a digoxin level. Other factors such as cross-reacting molecules, the effect of other biochemical findings, and the effect of the digoxin antidote (anti-digoxin antibody fragments) on immunoassay results need to be considered in clinical settings where the results aren’t consistent with clinical findings. The laboratory is ideally placed to help with issues relating from these factors to digoxin level interpretation.