Overview
Digoxin is a cardiac glycoside used primarily for rate control in atrial fibrillation and treatment of heart failure. It increases myocardial contractility and slows atrioventricular conduction through inhibition of the sodium-potassium ATPase pump. The drug has a narrow therapeutic index requiring careful monitoring of serum levels.
Mechanism of Action
Digoxin inhibits the sodium-potassium ATPase pump in cardiac myocytes, leading to increased intracellular sodium and calcium concentrations. This enhances myocardial contractility (positive inotropic effect) and slows atrioventricular conduction (negative dromotropic effect) through vagal stimulation and direct effects on the cardiac conduction system.
Indications
- Treatment of mild to moderate heart failure
- Control of ventricular response rate in patients with chronic atrial fibrillation
Common Doses
- 0.125 mg
- 0.25 mg
Dosage
Dosing is individualized based on renal function, age, weight, and clinical response. Loading doses may be used for rapid digitalization, followed by maintenance doses. Serum digoxin levels should be monitored to maintain therapeutic range of 0.5-2.0 ng/mL.
Contraindications
- Ventricular fibrillation
- Known hypersensitivity to digoxin or other digitalis preparations
- Hypersensitivity reactions including unexplained rash, swelling of mouth/lips/throat, or difficulty breathing
Side Effects
- Cardiac arrhythmias
- Digoxin toxicity symptoms (nausea, vomiting, visual disturbances, confusion)
- Fatigue, weakness, dizziness
- Headache, rash
Interactions
- Narrow therapeutic index increases risk with drug interactions
- Requires increased monitoring of serum levels with co-prescribed medications
- Common interactions with diuretics, antiarrhythmics, calcium channel blockers, and antibiotics
Counseling Points
- Take exactly as prescribed at same time each day
- Do not double dose if missed
- Report symptoms of toxicity (nausea, vomiting, visual changes, dizziness)
- Regular monitoring of blood levels required
- Inform all healthcare providers about digoxin use
- Maintain consistent potassium levels as directed