Cardoxin Disease Interactions

Digoxin may enhance accessory pathway conduction in conditions such as the Wolff-Parkinson-White syndrome. Patients with Wolf-Parkinson-White syndrome that presents atrial fibrillation are at higher risk for ventricular fibrillation. Treatment with digoxin should be used with caution in these patients.

Digoxin slows sinoatrial and AV conduction, prolonging the PR interval. When treated with digoxin, patients with preexisting sinus node disease may develop severe sinus bradycardia or sinoatrial block, and patients with incomplete AV block may progress to advanced or complete heart block. In such patients, consideration should be given to the insertion of a pacemaker prior to initiating treatment with digoxin. Digoxin may be administered to patients with complete, stable AV block who have congestive heart failure, provided the block was not induced by cardiac glycosides.

Calcium and digoxin have additive inotropic effects. Therefore, hypercalcemia from any cause will predispose patients to digoxin toxicity and serious arrhythmias. Hypercalcemia should be corrected prior to initiating treatment with digoxin, and serum calcium levels should be monitored during therapy.

Hypocalcemia can nullify the effects of digoxin. The drug may be ineffective in hypocalcemic patients until serum calcium levels are restored to normal. Restore serum calcium levels prior to initiating therapy with digoxin to obtain maximum results when using digoxin.

Potassium and/or magnesium depletion sensitizes the myocardium to digoxin. In patients with hypokalemia or hypomagnesemia, digoxin toxicity may occur despite serum drug concentrations below 2.0 ng/mL. Therapy with digoxin should be administered cautiously in patients with or predisposed to potassium and/or magnesium deficiency, including patients on diuretic therapy; those with primary or secondary aldosteronism (may have low potassium levels); those with severe or prolonged diarrhea or vomiting; those with malnutrition; and renal dialysis patients. Electrolyte imbalances should be corrected prior to initiation of treatment. Serum potassium and magnesium concentrations should be monitored during therapy.

Patients with heart failure associated with preserved left ventricular systolic function, such as in restrictive cardiomyopathy, constrictive pericarditis, amyloid heart disease and acute cor pulmonale, may be particularly susceptible to experience decrease cardiac output. Therapy with digoxin should be administered cautiously in such patients. Patients with idiopathic hypertrophic subaortic stenosis may have worsening of the outflow obstruction due to the inotropic effects of digoxin.

Digoxin is primarily eliminated by the kidney. Patients with renal impairment may be at increased risk for digoxin toxicity, including ventricular arrhythmias and AV conduction disturbances, due to decreased drug clearance. Therapy with digoxin should be administered cautiously in patients with impaired renal function. Dosage adjustments should be made according to product package labeling and patient attributes such as age, ideal body weight, and other concomitant disease states and medication usage. Dosage increments should be made very gradually, since the elimination half-life may be prolonged in these patients and a longer period of time is required to establish steady-state serum concentrations than normal. These patients should be monitored closely for manifestations of toxicity, and dosages further adjusted as necessary. If toxicity occurs, clinicians should be aware that the adverse effects may also be prolonged.

Digoxin can rarely precipitate vasoconstriction and may promote the development of cytokines; therefore, should be avoided in patients with myocarditis.

The use of digoxin is contraindicated in patients with ventricular fibrillation. Digoxin toxicity is associated with adverse cardiac effects, including ventricular arrhythmias, which are most commonly seen in chronic toxicity. Digoxin-induced ventricular tachycardia is associated with a high mortality rate, since ventricular fibrillation or asystole may result. Therapy with digoxin should be administered cautiously in patients with frequent ventricular premature contractions or ventricular tachycardia, especially if these arrhythmias are not caused by heart failure.

The use of inotropic drugs in some patients with acute myocardial infarction may lead to increases in myocardial oxygen demand and lead to ischemia. Therapy with digoxin should be administered cautiously in these patients.

Heart failure and/or atrial arrhythmias resulting from hypermetabolic or hyperdynamic states such as hyperthyroidism, hypoxia, or arteriovenous shunt are best managed by treating the underlying condition. Atrial arrhythmias associated with hypermetabolic states are particularly refractory to digoxin, possibly due to altered pharmacokinetics. Specifically, the apparent volume of distribution and renal elimination of the drug may be increased, resulting in lower serum concentrations. Therapy with digoxin should be administered cautiously in patients with hyperthyroidism. Serum digoxin levels should be monitored regularly and dosage adjustments may be required secondary to changes in their thyroid condition.

Hypothyroidism may reduce the requirements for digoxin due to decreased volume of distribution and plasma clearance of the drug. Therapy with digoxin should be initiated at lower dosages in patients with hypothyroidism to avoid toxicity. Serum digoxin levels should be monitored regularly and dosage adjustments may be required secondary to changes in thyroid condition.

Patients with beri beri heart disease may fail to respond adequately to digoxin if the underlying thiamine deficiency is not treated concomitantly.