Monitor for signs and symptoms of digoxin toxicity and clinical response. Adjust dose based on toxicity, efficacy, and blood levels.
Serum digoxin levels less than 0.5 ng/mL have been associated with diminished efficacy, while levels above 2 ng/mL have been associated with increased toxicity without increased benefit.
Interpret the serum digoxin concentration in the overall clinical context, and do not use an isolated measurement of serum digoxin concentration as the basis for increasing or decreasing the DIGITEK ® (digoxin tablets) dose. Serum digoxin concentrations may be falsely elevated by endogenous digoxin-like substances [see Drug Interactions (7.4)]. If the assay is sensitive to these substances, consider obtaining a baseline digoxin level before starting DIGITEK ® (digoxin tablets) and correct post-treatment values by the reported baseline level.
Obtain serum digoxin concentrations just before the next scheduled DIGITEK ® (digoxin tablets) dose or at least 6 hours after the last dose. The digoxin concentration is likely to be 10-25% lower when sampled right before the next dose (24 hours after dosing) compared to sampling 8 hours after dosing (using once-daily dosing). However, there will be only minor differences in digoxin concentrations using twice daily dosing whether sampling is done at 8 or 12 hours after a dose.
When switching from intravenous to oral digoxin formulations, make allowances for differences in bioavailability when calculating maintenance dosages (see Table 6).
Equivalent Doses (mcg)
DIGITEK ® (digoxin tablets)
Digoxin Intravenous Injection
DIGITEK ® (digoxin tablets, USP) is available containing 125 mcg (0.125 mg) or 250 mcg (0.25 mg) of digoxin, USP.
- The 125 mcg (0.125 mg) tablets are yellow, round, scored, slope-faced tablets debossed with M above the score and 145 below the score on one side of the tablet and blank on the other side.
- The 250 mcg (0.25 mg) tablets are white, round, scored, slope-faced tablets debossed with M above the score and 147 below the score on one side of the tablet and blank on the other side.
DIGITEK ® (digoxin tablets) is contraindicated in patients with:
- Ventricular fibrillation [see Warnings and Precautions (5.1)]
- Known hypersensitivity to digoxin (reactions seen include unexplained rash, swelling of the mouth, lips or throat or a difficulty in breathing). A hypersensitivity reaction to other digitalis preparations usually constitutes a contraindication to digoxin.
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.
Digoxin may cause severe sinus bradycardia or sino-atrial 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.
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 (6) and Overdosage (10)]. 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.
It may be desirable to reduce the dose of or discontinue digoxin for 1 to 2 days prior to electrical cardioversion of atrial fibrillation to avoid the induction of ventricular arrhythmias, but physicians must consider the consequences of increasing the ventricular response if digoxin is decreased or withdrawn. If digitalis toxicity is suspected, elective cardioversion should be delayed. If it is not prudent to delay cardioversion, the lowest possible energy level should be selected to avoid provoking ventricular arrhythmias.
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