What are the contraindications of digoxin (digitalis glycoside)?

Contraindications of Digoxin

Digoxin is absolutely contraindicated in patients with ventricular fibrillation, known hypersensitivity to digoxin or other digitalis preparations, significant sinus or atrioventricular block without a permanent pacemaker, and pre-excitation syndromes such as Wolff-Parkinson-White syndrome with atrial fibrillation. 1, 2, 3

Absolute Contraindications

Cardiac Conduction Disorders

• Ventricular fibrillation is an absolute contraindication per FDA labeling 1
• Second- or third-degree AV block without a permanent pacemaker 2, 3
• Sick sinus syndrome and carotid sinus syndrome 2
• Patients should not receive digoxin if they have significant sinus or atrioventricular block unless the block has been addressed with a permanent pacemaker 2

Pre-excitation Syndromes

• Wolff-Parkinson-White syndrome with atrial fibrillation or atrial flutter is contraindicated because digoxin can accelerate conduction through the accessory pathway, potentially causing ventricular fibrillation 2, 3

Hypersensitivity

• Known hypersensitivity to digoxin or any digitalis preparation 1
• A hypersensitivity reaction to other digitalis preparations usually constitutes a contraindication to digoxin 1

Structural Heart Disease

• Hypertrophic obstructive cardiomyopathy is a contraindication 2

Relative Contraindications and Situations Requiring Extreme Caution

Electrolyte Abnormalities

• Hypokalemia significantly increases the risk of digoxin toxicity and arrhythmias, even at therapeutic digoxin levels 2, 3
• Hypercalcemia potentiates digoxin's cardiac effects 2
• Hypomagnesemia increases toxicity risk 2, 3
• Toxicity may occur with therapeutic digoxin levels if these electrolyte abnormalities coexist 2, 4

Concomitant Medications

• Use cautiously with other drugs that depress sinus or atrioventricular nodal function (amiodarone, beta-blockers, calcium channel blockers) 2, 4
• The drug should be used cautiously in patients taking other drugs that can affect digoxin levels or cardiac conduction, even though such patients usually tolerate digoxin without difficulty 2

Renal Impairment

• Not an absolute contraindication, but requires significant dose reduction 2, 3, 5
• Digoxin elimination is primarily renal, and impaired renal function elevates serum levels and increases toxicity risk 2
• For marked renal impairment (CrCl <30 mL/min), use 0.0625 mg daily 5

Age and Body Composition

• Elderly patients (>70 years) and those with low lean body mass require lower doses (0.125 mg daily or every other day) due to altered pharmacokinetics 2, 3, 4
• These are not contraindications but require careful dosing adjustments 2

Clinical Context: When NOT to Use Digoxin

Acute Heart Failure

• Digoxin is not indicated as primary treatment for acutely decompensated heart failure 4
• It may be initiated after emergent treatment has been completed as part of long-term strategy 4

Left Ventricular Failure with Specific Features

• Verapamil (not digoxin itself) is contraindicated in LV failure with pulmonary congestion or LVEF <40%, which is relevant when considering combination therapy 2

Critical Monitoring to Prevent Toxicity

Signs of Digoxin Toxicity (Requiring Immediate Evaluation)

• Cardiac arrhythmias (ectopic beats, re-entrant rhythms, heart block) 2, 3
• Gastrointestinal symptoms (anorexia, nausea, vomiting) 2, 3
• Neurological complaints (visual disturbances, disorientation, confusion) 2, 3
• Overt toxicity is commonly associated with serum levels >2 ng/mL 2

Conditions That Lower the Threshold for Toxicity

• Hypothyroidism increases sensitivity to digoxin 2, 4
• In toxic states (serum levels >2 ng/mL), digoxin is proarrhythmic and can aggravate heart failure, particularly with coexistent hypokalemia 2

Common Pitfall to Avoid

The most dangerous clinical scenario is using digoxin in a patient with pre-excitation syndrome (WPW) and atrial fibrillation, as this can precipitate ventricular fibrillation by accelerating conduction through the accessory pathway 2, 3. Always obtain an ECG before initiating digoxin to rule out pre-excitation patterns.