Digoxin - Warnings and Precautions

5 WARNINGS AND PRECAUTIONS Risk of rapid ventricular response leading to ventricular fibrillation in patients with AV accessory pathway.

Risk of advanced or complete heart block in patients with sinus node disease and AV block.

Digoxin toxicity: Indicated by nausea, vomiting, visual disturbances, and cardiac arrhythmias.

Advanced age, low body weight, impaired renal function and electrolyte abnormalities predispose to toxicity.

Risk of ventricular arrhythmias during electrical cardioversion.

Not recommended in patients with acute myocardial infarction.

Avoid digoxin in patients with myocarditis.

5.1 Ventricular Fibrillation in Patients With Accessory AV Pathway (Wolff-Parkinson-White Syndrome) Patients with Wolff-Parkinson-White syndrome who develop atrial fibrillation are at high risk of ventricular fibrillation.

Treatment of these patients with digoxin leads to greater slowing of conduction in the atrioventricular node than in accessory pathways, and the risks of rapid ventricular response leading to ventricular fibrillation are thereby increased.

5.2 Sinus Bradycardia and Sino-atrial Block Digoxin may cause severe sinus bradycardia or sinoatrial block particularly in patients with pre-existing sinus node disease and may cause advanced or complete heart block in patients with pre-existing incomplete AV block.

Consider insertion of a pacemaker before treatment with digoxin.

5.3 Digoxin Toxicity Signs and symptoms of digoxin toxicity include anorexia, nausea, vomiting, visual changes and cardiac arrhythmias [first-degree, second-degree (Wenckebach), or third-degree heart block (including asystole); atrial tachycardia with block; AV dissociation; accelerated junctional (nodal) rhythm; unifocal or multiform ventricular premature contractions (especially bigeminy or trigeminy); ventricular tachycardia; and ventricular fibrillation].

Toxicity is usually associated with digoxin levels greater than 2 ng/ml although symptoms may also occur at lower levels.

Low body weight, advanced age or impaired renal function, hypokalemia, hypercalcemia, or hypomagnesemia may predispose to digoxin toxicity.

Obtain serum digoxin levels in patients with signs or symptoms of digoxin therapy and interrupt or adjust dose if necessary [see Adverse Reactions and Overdosage ].

Assess serum electrolytes and renal function periodically.

The earliest and most frequent manifestation of digoxin toxicity in infants and children is the appearance of cardiac arrhythmias, including sinus bradycardia.

In children, the use of digoxin may produce any arrhythmia.

The most common are conduction disturbances or supraventricular tachyarrhythmias, such as atrial tachycardia (with or without block) and junctional (nodal) tachycardia.

Ventricular arrhythmias are less common.

Sinus bradycardia may be a sign of impending digoxin intoxication, especially in infants, even in the absence of first-degree heart block.

Any arrhythmias or alteration in cardiac conduction that develops in a child taking digoxin should initially be assumed to be a consequence of digoxin intoxication.

Given that adult patients with heart failure have some symptoms in common with digoxin toxicity, it may be difficult to distinguish digoxin toxicity from heart failure.

Misidentification of their etiology might lead the clinician to continue or increase digoxin dosing, when dosing should actually be suspended.

When the etiology of these signs and symptoms is not clear, measure serum digoxin levels.