Digoxin is used to treat supraventricular tachyarrhythmias and congestive heart failure. Other cardiac glycosides are found in plants such as foxglove, oleander, and lily of the valley.
Toxicity can occur following acute ingestion or develop during chronic therapy (Table 108-1). Acute toxicity typically presents with nausea, vomiting, or abdominal pain. Characteristic cardiac effects include bradyarrhythmias and/or supraventricular tachycardia with atrioventricular block. Severe toxicity can result in ventricular arrhythmias. Chronic toxicity is more common in the elderly and often occurs as a result of concomitant illness (heart disease, renal/liver failure, hypothyroidism, chronic obstructive pulmonary disease), electrolyte abnormality (hypokalemia, hypomagnesemia), or drug interactions (quinidine, amiodarone, spironolactone, calcium channel blockers, macrolide antibiotics). Neuropsychiatric symptoms are more common with chronic toxicity, though cardiac effects are similar to those seen with acute toxicity.
Table 108-1 Clinical Presentation of Digitalis Glycoside Toxicity ||Download (.pdf)
Table 108-1 Clinical Presentation of Digitalis Glycoside Toxicity
| Clinical history||Intentional or accidental ingestion|
| GI effects||Nausea and vomiting|
| Central nervous system effects||Headache, dizziness, confusion, coma|
| Cardiac effects||Bradyarrhythmias or supraventricular tachyarrhythmias with atrioventricular block|
| Electrolyte abnormalities||Hyperkalemia|
| Digoxin level||Marked elevation (if obtained within 6 h)|
| Clinical history||Typically in elderly cardiac patients taking diuretics; may have renal insufficiency|
| GI effects||Nausea, vomiting, diarrhea, abdominal pain|
| Central nervous system effects||Fatigue, weakness, confusion, delirium, coma|
| Cardiac effects||Almost any ventricular or supraventricular dysrhythmia can occur; ventricular dysrhythmias are common|
| Electrolyte abnormalities||Normal or decreased serum potassium, hypomagnesemia|
| Digoxin level||Minimally elevated or within “therapeutic” range|
Diagnosis and Differential
Hyperkalemia is often seen in acute poisoning, but may be absent in chronic toxicity. Serum digoxin levels are neither sensitive nor specific for toxicity. However, those patients with higher levels (>2 milligrams/mL) are more likely to experience toxicity. Almost any arrhythmia can occur with toxicity; however, the most common finding is premature ventricular beats. The differential diagnosis includes sinus node disease or toxicity from calcium channel blockers, β-blockers, class IA antidysrhythmics, clonidine, organophosphates, or other cardiotoxic plants.
Emergency Department Care and Disposition
All patients require continuous cardiac monitoring, intravenous (IV) access, and frequent reevaluation (Table 108-2).
Administer activated charcoal, 1 gram/kilogram in cases of acute ingestion.
Use atropine 0.5 to 2.0 milligrams (0.02 milligram/kilogram, minimum dose 0.1 milligram) IV to treat bradydysrhythmias.
Administer digoxin-specific Fab for ventricular dysrhythmias, hemodynamically significant bradydysrhythmias, and hyperkalemia greater than 5.5 mEq/L. Dosing of digoxin-specific Fab is calculated according to Table 108-3.
Treat ventricular dysrhythmias with phenytoin 15 milligrams/kilograms infused no faster than 25 milligrams/min; lidocaine 1 milligram/kilogram; or magnesium sulfate 2 to 4 grams (25 to 50 milligrams/kilograms) IV. Electro-cardioversion may induce refractory ventricular dysrhythmias and should be considered only as a last resort. The initial setting should be 10 to 25 J.