A case of divergent digitoxin values under treatment of a patient with acute digitoxin overdose with digitalis antibody fragments.

A 36 year old male was admitted to the intensive care unit with acute digitalis intoxication after ingestion of 350 digitoxin tablets (= 35 mg digitoxin). He was treated with Fab fragments of a digitalis antiserum raised in sheep, the concentrations of digitoxin in serum, urine and dialysates being measured with two automated digitoxin immunoassays based on fluorescence labelling techniques. Whereas one assay reflected the total digitoxin concentrations, including that bound to the antidote, the other measured only the bioactive "free" form of the drug. This article examines the use and limitations of both assay systems in assessing and monitoring cases of digitalis poisoning.