[Digitoxin poisoning: reversing ventricular fibrillation with Fab fragments of anti-digoxin antibody]

Area of Science:

• Immunology
• Pharmacology
• Toxicology

Background:

• Digitoxin overdose presents a significant clinical challenge with high mortality.
• Ovine anti-digoxin antibody fragments offer a potential antidote for cardiac glycoside poisoning.

Observation:

• A patient with severe digitoxin poisoning (10 mg ingested, serum level 265 µg/L, K+ 7.5 mEq/L) was treated with ovine anti-digoxin antibody fragments.
• Despite low in vitro cross-reactivity with digitoxin (6.85%), clinical improvement was observed with 3.6 g of the antibody fragments.

Findings:

• Treatment led to clinical recovery, reversal of ventricular fibrillation, and normalization of potassium levels.
• Serum digitoxin levels increased, indicating redistribution from tissues to plasma, and rapid urinary excretion of Fab-bound digitoxin was observed.
• These changes suggest reversible ATPase inhibition and a shift in digitoxin metabolism/elimination pathways.

Implications:

• Ovine anti-digoxin antibody fragments are effective in treating severe digitoxin poisoning, even with limited in vitro cross-reactivity.
• The treatment appears to reverse digitalis toxicity by altering drug distribution and promoting elimination.
• This approach highlights the therapeutic potential of targeted antibody fragment therapy in managing drug overdoses.