Digoxin overdose

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Digitalis is a medication prescribed to certain heart patients. Digitalis toxicity is a complication of digitalis therapy, or it may be occur when someone takes more than a large amount of the drug at one time.The most common prescription form of this medication is called digoxin. Digitoxin is another form of digitalis.

Historical Perspective

Digitalis, derived form the foxglove plant, Digitalis purpurea, is mentioned in writings as early as 1250; a Welsh family, known as the Physicians of Myddvai, collected different herbs and digitalis was included in their prescriptions. However, the drug was used erratically until the 18th century, when William Withering, an English physician and botanist, published a monograph describing the clinical effects of an extract of the foxglove plant. Later, in 1785, the indication and the toxicity of digitalis were reported in his book, "An account of the Foxglove and some of its medical uses with practical remarks on dropsy, and other diseases". In Denmark, the leaves of Digitalis purpurea or Digitalis lanata were tested for cardiac glycoside activity. The standardized digitalis powder was used in tinctures, infusions, and tablets. The preparations were included in successive editions of the Danish pharmacopoeia, some of the tinctures already in 1828, i.e. before the standardization of the drug.

Overdosage topics

Discontinuation

Potassium salts

Dialysis/exchange transfusion/cardiopulmonary bypass

Activated charcoal

Digoxin Immune Fab

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Diagnosis

Electrocardiographic Findings

• Bradyarrhythmias:

• AV block may be present including complete AV block and Wenkebach.

• Tachyarrhythmias:

• Junctional tachycardia
• Atrial tachycardia
• Ventricular ectopic beats
• Ventricular bigeminy
• Monomorphic ventricular tachycardia
• Bidirectional ventricular tachycardia

• Arrhythmias:

• If digoxin levels are extremely high, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation may develop.

It should be noted that the electrocardiographic effects of dig toxicity are increased by hypokalemia.

Discontinuation

Digoxin should be discontinued until all signs of toxicity are gone. Discontinuation may be all that is necessary if toxic manifestations are not severe and appear only near the expected time for maximum effect of the drug. Return to top

Potassium salts

There has been one reported case of massive overdosage with Nifedipine extended-release tablets. The main effects of ingestion of approximately 4800 mg of Nifedipine extended-release in a young man attempting suicide as a result of cocaine-induced depression was initial dizziness, palpitations, flushing, and nervousness. Within several hours of ingestion, nausea, vomiting, and generalized edema developed. No significant hypotension was apparent at presentation, 18 hours post-ingestion. Electrolyte abnormalities consisted of a mild, transient elevation of serum creatinine, and modest elevations of LDH and CPK, but normal SGOT. Vital signs remained stable, no electrocardiographic abnormalities were noted and renal function returned to normal within 24 to 48 hours with routine supportive measures alone. No prolonged sequelae were observed.Potassium salts may be used, particularly if hypokalemia is present. Potassium chloride in divided oral doses totaling 1 to 1.5 mEq K+ per kilogram (kg) body weight may be given provided renal function is adequate (1 gram of potassium chloride contains 13.4 mEq K+). When correction of the arrhythmia with potassium is urgent and the serum potassium concentration is low or normal, approximately 0.5 mEq/kg of potassium per hour may be given intravenously in 5% dextrose injection. The intravenous solution of potassium should be dilute enough to avoid local irritation; however, especially in infants care must be taken to avoid intravenous fluid overload. ECG monitoring should be performed to watch for any evidence of potassium toxicity (e.g., peaking of T waves) and to observe the effect on the arrhythmia. The infusion may be stopped when the desired effect is achieved.
Note: Potassium should not be used and may be dangerous in heart block due to Digoxin, unless primarily related to supraventricular tachycardia. Return to top

Dialysis/exchange transfusion/cardiopulmonary bypass

Because of its large extravascular volume of distribution, Digoxin is not effectively removed from the body by dialysis, by exchange transfusion, or during cardiopulmonary bypass. Return to top

Activated charcoal

Multiple doses of activated charcoal have been found effective in at least 1 case report, and may be of use while the need for and availability of Digoxin specific antibody fragments are being assessed. In advanced heart block, temporary ventricular pacing may be beneficial. Return to top

Digoxin Immune Fab

Digoxin Immune Fab (Ovine) [DIGIBIND®, DIGIFAB®] may be indicated for the treatment of patients with life-threatening or potentially life-threatening Digoxin toxicity or overdose. Return to top

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Adapted from the FDA Package Insert.