Lanoxin (digoxin) is a time-tested cardiac glycoside derived from the Digitalis lanata plant, prescribed for the management of specific heart conditions. It functions primarily by increasing the force of myocardial contractions and modulating the electrical conduction system of the heart. This agent remains a cornerstone in therapeutic regimens for atrial fibrillation and heart failure when appropriate patient selection and vigilant monitoring are employed. Its narrow therapeutic index necessitates careful dosing and consistent clinical oversight to maximize efficacy and minimize risks.

Features

• Contains digoxin as the active pharmaceutical ingredient
• Available in oral tablet (125 mcg and 250 mcg) and injectable formulations
• Exhibits positive inotropic and negative chronotropic effects
• Characterized by a long half-life, permitting once-daily dosing in most cases
• Requires therapeutic drug monitoring (TDM) for optimal dosing

Benefits

• Enhances cardiac output in patients with systolic heart failure, improving exercise tolerance and reducing symptoms like dyspnea and fatigue
• Provides effective rate control in atrial fibrillation and atrial flutter, helping to stabilize ventricular response
• Reduces hospitalizations related to heart failure exacerbations when used as part of a comprehensive treatment plan
• Offers flexible administration routes, including IV for acute settings and oral for maintenance therapy
• Functions independently of beta-adrenergic receptor activity, making it useful in patients on beta-blockers or with compromised sympathetic response

Common use

Lanoxin is indicated for the treatment of mild to moderate heart failure, particularly in patients with reduced ejection fraction, and for controlling ventricular rate in patients with chronic atrial fibrillation. It is often incorporated into treatment plans alongside diuretics, ACE inhibitors, and beta-blockers. Its use is generally reserved for symptomatic patients who have not achieved adequate control with first-line agents alone.

Dosage and direction

Dosing must be individualized based on renal function, age, weight, and concomitant medications. A typical digitalizing dose in adults with normal renal function is 0.75–1.5 mg administered orally in divided doses over 24 hours, followed by a maintenance dose of 0.125–0.25 mg daily. In elderly patients or those with renal impairment, doses are often reduced. Serum digoxin concentrations should be maintained between 0.5–0.9 ng/mL for heart failure and up to 1.2 ng/mL for atrial fibrillation, though clinical response should guide therapy above absolute levels. Administration with food may slightly delay absorption but does not significantly affect bioavailability.

Precautions

Renal impairment significantly prolongs digoxin elimination—dosage adjustments and frequent monitoring are essential. Electrolyte disturbances, particularly hypokalemia, hypomagnesemia, and hypercalcemia, increase the risk of toxicity. Thyroid dysfunction alters digoxin sensitivity; hypothyroidism may reduce requirements, while hyperthyroidism may increase them. Use with caution in patients with acute myocardial infarction, sinus node disease, or Wolff-Parkinson-White syndrome. Periodic assessment of renal function, electrolytes, and digoxin levels is mandatory.

Contraindications

Lanoxin is contraindicated in patients with ventricular fibrillation or known hypersensitivity to digoxin or other digitalis preparations. It should not be used in patients with second- or third-degree AV block (in absence of a functioning pacemaker), idiopathic hypertrophic subaortic stenosis, or constrictive pericarditis. Concomitant use with intravenous calcium may precipitate serious arrhythmias and is contraindicated.

Possible side effect

Common adverse effects include nausea, vomiting, diarrhea, headache, dizziness, and visual disturbances such as yellow-green halos (chromatopsia). Serious side effects involve cardiac arrhythmias (e.g., PVCs, AV block, atrial tachycardia with block, ventricular tachycardia), confusion, fatigue, and rash. Toxicity may occur even at therapeutic levels, particularly in the setting of electrolyte imbalances.

Drug interaction

Diuretics (especially loop and thiazide types) may cause hypokalemia, increasing digoxin toxicity risk. Quinidine, verapamil, amiodarone, cyclosporine, and macrolide antibiotics can increase serum digoxin concentrations. Concomitant use with sympathomimetics, calcium channel blockers, or beta-blockers may potentiate bradycardia or AV block. Antacids, cholestyramine, and certain antineoplastics may decrease digoxin absorption.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next dose. Doubling the dose is not recommended. Patients should maintain a regular dosing schedule and inform their healthcare provider if multiple doses are missed, as this may necessitate re-titration.

Overdose

Digoxin overdose is a medical emergency manifesting as severe nausea, vomiting, hyperkalemia, and life-threatening arrhythmias. Administer activated charcoal if ingestion was recent. Digoxin immune fab (Digibind®) is the specific antidote for serious toxicity. Supportive care includes correcting electrolyte abnormalities and managing arrhythmias with medications such as lidocaine or phenytoin. Avoid calcium administration in hyperkalemic patients, as it may worsen cardiotoxicity.

Storage

Store at room temperature (15–30°C), protected from light and moisture. Keep all medications out of reach of children and pets. Do not use beyond the expiration date printed on the packaging.

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, changing, or discontinuing any medication. Dosage and indications may vary based on individual patient factors and latest clinical guidelines.

Reviews

Clinical studies and decades of use support Lanoxin’s efficacy in rate control and systolic heart failure, though its narrow therapeutic window demands careful management. Many cardiologists regard it as a valuable option in select patients, particularly those with comorbid atrial fibrillation and heart failure. Patient response varies; some report significant symptomatic improvement, while others experience side effects requiring discontinuation. Ongoing monitoring and patient education are critical to its safe and effective use.