Influence of assay methods on serum concentrations of digoxin during FAB fragment treatment

Free and total digoxin in serum during treatment of acute digoxin poisoning with Fab fragments: case study

A woman ingested 10 mg of methyldigoxin in a suicide attempt and presented 19 hours after ingestion with clinical signs of glycoside intoxication. Her serum level of digoxin was 7.4 ng/mL, and antidotal therapy with Fab antibody fragments was started. The manufacturer's recommended dosing scheme was modified, with 80 mg Fab administered intravenously within 15 minutes followed by a continuous infusion at 30 mg/h. Total serum concentration of digoxin increased markedly within minutes after Fab therapy was started, while the level of free digoxin immediately decreased into the nontoxic range without recrudescent toxic effects of digoxin. The cumulative amounts of free and bound digoxin that were excreted in urine within 30 hours after ingestion were 900 microg and 1600 microg, respectively. Half-life of bound digoxin in urine was 9.9 hours; mean rate of clearance of bound digoxin in the urine was 7.0 mL/min. On the basis of these kinetic data, a smaller initial bolus dose of Fab followed by a continuous infusion may be a more tailored, cost-effective, and relatively safe therapy for patients who have overdosed on cardiac glycosides.

Serum digoxin in the presence of Digibind: determination of digoxin by the Abbott AxSYM and Baxter Stratus II immunoassays by direct analysis without pretreatment of serum samples

We have reevaluated the feasibility of using direct immunochemical methods to track free digoxin in patients receiving Digibind®. We report here that results obtained by the Stratus II and AxSYM immunoassays on patients receiving digoxin (without Digibind), digoxin-fortified serum samples supplemented with Digibind, and a digitoxic patient treated with Digibind, show no clinically significant biases. We conclude that useful free digoxin concentrations may be obtained for Digibind-treated patients using either the AxSYM or Stratus immunoassays without subjecting samples to ultrafiltration before analysis.

Treatment of toad venom poisoning with digoxin-specific Fab fragments

Toxicity from toad venom poisoning is similar to digoxin toxicity and carries a high mortality rate. We report on six previously healthy men who developed vomiting and bradycardia after ingesting a purported topical aphrodisiac. Each patient had positive apparent digoxin levels and the first four patients died of cardiac dysrhythmias. The last two patients recovered following treatment with digoxin Fab fragments. We analyzed samples of the purported aphrodisiac and found that it was identical to Chan Su, a Chinese medication made from toad venom. To our knowledge, this is the first reported use of digoxin Fab fragments to treat toad venom poisoning.