Digoxin

Digoxin inhibits the Na+/K+-ATPase pump in myocardial cells, leading to increased intracellular sodium. This in turn reduces the activity of the Na+/Ca++ exchanger, increasing intracellular calcium concentration. The elevated calcium enhances myocardial contractility (positive inotropy) and prolongs the effective refractory period of the AV node, thus slowing ventricular rate in atrial fibrillation. It also increases vagal tone.

Adult

Digitalization (Rapid): 0.25-0.5 mg IV/oral loading dose, followed by 0.125-0.25 mg every 6-8 hours until desired effect (total 0.75-1.5 mg over 24 hours). Maintenance: 0.125-0.25 mg orally once daily, adjusted based on clinical response and serum levels (target 0.5-2 ng/mL).

Pediatric

Neonates: 10-30 mcg/kg oral loading dose (split over 24h); maintenance 5-10 mcg/kg/day. Infants (1 month-2 years): 30-50 mcg/kg oral loading; maintenance 10-15 mcg/kg/day. Children (>2 years): 20-35 mcg/kg oral loading; maintenance 5-10 mcg/kg/day. Doses are total cumulative for loading, given in divided doses over 24 hours, followed by daily maintenance. Adjust based on clinical response.

Renal adjustment

Critically important. Reduce dose or frequency based on creatinine clearance (CrCl). For CrCl 10-50 mL/min, administer 25-75% of usual dose or extend dosing interval. For CrCl <10 mL/min, administer 10-25% of usual dose or extend interval significantly (e.g., every 3-5 days). Monitor serum levels closely.

Hepatic adjustment

No dosage adjustment is typically required as hepatic metabolism is minimal.

Geriatric

Start with lower doses (e.g., 0.0625-0.125 mg daily) due to age-related decline in renal function and increased sensitivity. Monitor closely for toxicity.

Max dose

Not a strict maximum dose; doses rarely exceed 0.25 mg daily for maintenance in adults with normal renal function, aiming for a therapeutic serum level of 0.5-2 ng/mL.

• Ventricular fibrillation
• Hypersensitivity to digoxin or other digitalis preparations
• Ventricular tachycardia (unless due to congestive heart failure)
• Second- or third-degree AV block (without a pacemaker)
• Hypertrophic obstructive cardiomyopathy (HOCM) unless to treat atrial fibrillation and severe CHF
• Wolff-Parkinson-White syndrome with atrial fibrillation (risk of accelerated conduction down accessory pathway)
• Sinus or AV node dysfunction
• Wolff-Parkinson-White syndrome (risk of extremely rapid rate if atrial fibrillation develops)
• Aged are relatively intolerant
• Do not give full loading dose if patient received within past week
• hypokalemia
• myocardial ischaemia
• thyrotoxicosis
• ventricular tachycardia
• partial A-V block
• acute myocarditis (diphtheria, acute rheumatic carditis, toxic carditis)
• wolff-parkinson-white syndrome