Za Pharmacy
Drugs, Supplies and Delivery
Digoxin
Digoxin is a cardiac glycoside that has been used for centuries to manage heart failure and atrial fibrillation. Despite the advent of newer medications, digoxin remains a valuable therapeutic option due to its unique mechanism of action and clinical benefits. This article synthesizes information from the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of digoxin, including its mechanism, uses, dosing, side effects, precautions, and drug interactions.
Digoxin exerts its effects through two primary mechanisms:
- Positive Inotropic Effect:
- Digoxin inhibits the Na-K-ATPase pump in cardiac myocytes, leading to increased intracellular sodium levels. This results in a secondary increase in intracellular calcium via the Na-Ca exchanger, enhancing myocardial contractility (Lippincott, Lange).
- Negative Chronotropic Effect:
- Digoxin increases vagal tone and reduces conduction through the atrioventricular (AV) node, making it effective in controlling ventricular rate in atrial fibrillation (BNF).
- Heart Failure with Reduced Ejection Fraction (HFrEF):
- Improves symptoms and reduces hospitalizations in patients with HFrEF, particularly in those with persistent symptoms despite optimal therapy (BNF).
- Atrial Fibrillation (AF):
- Controls ventricular rate in AF by slowing AV nodal conduction (Lippincott).
- Heart Failure:
- Loading dose (if rapid digitalization is needed): 0.75–1.5 mg in divided doses over 24 hours.
- Maintenance dose: 125–250 mcg once daily (adjust based on renal function and serum digoxin levels) (BNF).
- Atrial Fibrillation:
- Maintenance dose: 62.5–250 mcg once daily (adjust based on heart rate response and serum levels) (Lippincott).
Administration:
- Can be taken with or without food.
- Regular monitoring of serum digoxin levels (therapeutic range: 0.5–2.0 ng/mL) is essential to avoid toxicity (Lange).
- Common: Nausea, vomiting, anorexia, and fatigue (Lippincott).
- Serious: Cardiac arrhythmias (e.g., bradycardia, AV block, ventricular tachycardia), visual disturbances (e.g., yellow-green halos), and confusion (BNF).
- Renal Impairment: Digoxin is primarily excreted by the kidneys; reduce dose in patients with renal dysfunction (Lange).
- Electrolyte Imbalances: Hypokalemia, hypomagnesemia, and hypercalcemia increase the risk of digoxin toxicity (Lippincott).
- Pregnancy: Use only if benefits outweigh risks; monitor closely (BNF).
- Contraindications: Ventricular fibrillation, hypertrophic obstructive cardiomyopathy (HOCM), and Wolff-Parkinson-White (WPW) syndrome (Lange).
- Diuretics: Thiazides and loop diuretics can cause hypokalemia, increasing the risk of digoxin toxicity (BNF).
- Amiodarone: Increases digoxin levels by reducing renal clearance; reduce digoxin dose by 50% (Lippincott).
- Calcium Channel Blockers (e.g., verapamil): Increase digoxin levels and risk of toxicity (Lange).
- Antibiotics (e.g., erythromycin, tetracycline): Alter gut flora, increasing digoxin absorption (BNF).
Digoxin is the generic name for this medication. It is marketed under the brand name Lanoxin® in some regions. Generic versions are widely available and cost-effective
