Digoxin Drug Profile

What is Digoxin?

Digoxin is a cardiac glycoside medication derived from the foxglove plant that has been used to treat heart conditions for over 200 years. It belongs to a class of drugs that affect the heart’s electrical conduction system and muscle contractions. Digoxin is primarily prescribed to treat heart failure and certain irregular heart rhythms, particularly atrial fibrillation.

Uses

Digoxin has several established medical uses for cardiovascular conditions:

• Heart failure: Helps improve symptoms and quality of life in patients with reduced ejection fraction by strengthening heart muscle contractions
• Atrial fibrillation: Controls heart rate by slowing electrical conduction through the heart’s natural pacemaker
• Atrial flutter: Similar to atrial fibrillation, helps regulate rapid, irregular heartbeats
• Paroxysmal supraventricular tachycardia: Used in certain cases to control episodes of rapid heart rate originating above the ventricles
• Rate control in chronic heart conditions: Maintains appropriate heart rate in patients with persistent arrhythmias

How it works

Digoxin works by inhibiting the sodium-potassium pump in heart muscle cells, which leads to increased calcium availability inside the cells. This increased calcium enhances the force of heart muscle contractions, making the heart pump more effectively. Additionally, digoxin slows electrical conduction through the atrioventricular node, which helps control heart rate in conditions like atrial fibrillation.

Side effects

Common side effects include:

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• Nausea and vomiting
• Loss of appetite
• Diarrhea
• Dizziness
• Headache
• Fatigue and weakness
• Visual disturbances (blurred or yellow vision)
• Confusion or mental changes

Serious side effects requiring immediate medical attention:

• Severe irregular heartbeat or very slow heart rate
• Signs of digoxin toxicity (severe nausea, vision changes, confusion)
• Chest pain or shortness of breath
• Fainting or severe dizziness
• Severe abdominal pain

Warnings and precautions

• Narrow therapeutic window: The difference between an effective dose and a toxic dose is small, requiring careful monitoring and regular blood level checks
• Kidney function: Patients with reduced kidney function need dose adjustments since digoxin is primarily eliminated through the kidneys
• Electrolyte imbalances: Low potassium, low magnesium, or high calcium levels can increase the risk of digoxin toxicity
• Elderly patients: Older adults are more sensitive to digoxin’s effects and may require lower doses
• Pregnancy and breastfeeding: Digoxin crosses the placenta and passes into breast milk; use only when benefits outweigh risks under medical supervision

Interactions

Digoxin has numerous significant drug interactions that can affect its levels or increase toxicity risk:

• Diuretics: Can cause potassium loss, increasing digoxin toxicity risk
• Amiodarone: Significantly increases digoxin levels, requiring dose reduction
• Quinidine: Doubles digoxin blood levels by reducing kidney elimination
• Verapamil and diltiazem: Calcium channel blockers that can increase digoxin levels
• Antibiotics (clarithromycin, erythromycin): May increase digoxin absorption and blood levels
• Antacids and kaolin-pectin: Can reduce digoxin absorption when taken together
• St. John’s wort: May decrease digoxin levels by increasing metabolism
• ACE inhibitors and ARBs: Can increase potassium levels, affecting digoxin’s effects

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Dosage

Digoxin dosing is highly individualized based on patient factors including age, kidney function, body weight, and the specific condition being treated. Typical adult maintenance doses range from 0.125 to 0.25 mg once daily, though some patients may require doses as low as 0.0625 mg or as high as 0.5 mg daily. Initial loading doses, when used, are typically calculated based on body weight and desired blood levels. Elderly patients and those with kidney problems usually require lower doses. Regular monitoring of blood levels, kidney function, and electrolytes is essential. All dosing decisions should be made by a healthcare provider who will consider individual patient factors and monitor for effectiveness and toxicity.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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