1. Introduction
Digoxin is a cardiac glycoside used to manage heart conditions such as atrial fibrillation and heart failure. It enhances myocardial contractility by inhibiting the sodium-potassium ATPase pump, increasing intracellular calcium levels, and improving cardiac output. Additionally, it slows conduction through the atrioventricular (AV) node, controlling heart rate in atrial fibrillation.
2. Indications
- Approved Indications:
- Heart failure with reduced ejection fraction (HFrEF), particularly in patients with persistent symptoms despite optimal therapy.
- Rate control in atrial fibrillation and atrial flutter.
- Off-Label Uses:
- Management of supraventricular tachycardias (SVTs).
3. Dosage
- Adults:
- Heart Failure: 125–250 mcg once daily. Adjust based on renal function and response.
- Atrial Fibrillation: 125–500 mcg once daily, titrated according to clinical response and serum levels.
- Children:
- Loading dose: 10–15 mcg/kg (given in divided doses over 24 hours).
- Maintenance dose: 2.5–5 mcg/kg/day in divided doses, adjusted by age and renal function.
- Renal Impairment:
- Dose reduction is necessary, as digoxin is primarily renally excreted.
4. Administration
- Take orally with water, with or without food.
- For IV administration, inject slowly over at least 5 minutes.
- Avoid rapid IV administration, as it may lead to arrhythmias.
5. Forms Available
- Tablets: 62.5 mcg, 125 mcg, 250 mcg.
- Oral solution: 50 mcg/mL.
- Intravenous solution: 250 mcg/mL.
6. Side Effects
6.1. Common Side Effects
- Nausea and vomiting.
- Dizziness or fatigue.
- Visual disturbances (e.g., blurred vision, yellow-green halos).
6.2. Less Common Side Effects
- Bradycardia.
- Confusion or mental disturbances.
6.3. Rare but Serious Side Effects
- Ventricular arrhythmias.
- Digoxin toxicity, particularly in patients with renal impairment.
7. Warnings
- Digoxin Toxicity: Narrow therapeutic index; toxicity may occur with serum levels >2 ng/mL or at lower levels in susceptible patients. Symptoms include nausea, confusion, arrhythmias, and visual disturbances.
- Electrolyte Imbalances: Hypokalaemia, hypomagnesaemia, and hypercalcaemia increase the risk of toxicity.
- Renal Impairment: Digoxin clearance is reduced; dosage adjustment is critical.
8. Precautions
- Monitor for signs of toxicity, especially in elderly patients or those with impaired renal function.
- Use with caution in patients with sick sinus syndrome or AV block.
- Avoid use in patients with Wolff-Parkinson-White syndrome and pre-excitation syndromes.
9. Interactions
- Drug-Drug Interactions:
- Diuretics: Increase risk of hypokalaemia and toxicity.
- Amiodarone, verapamil, and quinidine: Increase digoxin levels.
- Rifampin and phenytoin: Reduce digoxin levels.
- Drug-Food Interactions:
- High-fibre meals may reduce digoxin absorption.
10. Monitoring Parameters
- Serum digoxin levels (therapeutic range: 0.5–2 ng/mL).
- Renal function (e.g., serum creatinine, estimated glomerular filtration rate).
- Electrolytes (potassium, magnesium, calcium).
- Heart rate and rhythm (ECG monitoring if indicated).
11. Use in Children
- Safe for use in children when dosed appropriately. Close monitoring is required due to the narrow therapeutic window.
12. Use in Pregnancy
- Category C: Use only if the benefits outweigh the risks. No evidence of teratogenic effects, but toxicity may cause maternal and foetal complications.
13. Use in Elderly
- Use with caution due to increased risk of toxicity. Start at the lowest effective dose and monitor renal function and serum levels closely.
14. Use in Kidney Disease
- Dose adjustments are essential in renal impairment due to reduced clearance. Toxicity is more likely in patients with poor renal function.
15. Use in Liver Disease
- No specific dose adjustment is required for hepatic impairment, as digoxin is primarily renally excreted.
16. Patient Counselling Points
- Take digoxin exactly as prescribed. Do not take extra doses to make up for missed doses.
- Report symptoms of toxicity, such as nausea, vomiting, visual changes, or irregular heartbeats, immediately.
- Avoid high-fibre meals close to taking your dose, as they may reduce absorption.
- Inform your healthcare provider of all other medications, including over-the-counter drugs and supplements.
- Keep regular follow-up appointments for blood tests and ECGs.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Lanoxin | GlaxoSmithKline | $20–40 (30 tablets, 125 mcg) |
Digitek | UCB Pharma | $15–30 (30 tablets, 125 mcg) |
Generic Digoxin | Various | $10–20 (30 tablets, 125 mcg) |
18. FAQs (15 Questions)
- What is digoxin used for?
Digoxin is used to manage heart failure and control heart rate in atrial fibrillation. - How does digoxin work?
It increases the force of heart contractions and slows the heart rate by inhibiting the sodium-potassium ATPase pump. - What are the common side effects of digoxin?
Nausea, vomiting, dizziness, and visual disturbances are common. - How should digoxin be taken?
Take it orally with water, at the same time each day. Avoid high-fibre meals close to dosing. - What are the signs of digoxin toxicity?
Symptoms include nausea, confusion, irregular heartbeats, and yellow-green vision changes. - Can digoxin be stopped suddenly?
No, abrupt discontinuation may worsen heart failure or arrhythmias. Consult your doctor before stopping. - How is digoxin monitored?
Serum digoxin levels, kidney function, electrolytes, and heart rate are routinely monitored. - Can digoxin interact with other medications?
Yes, it interacts with diuretics, amiodarone, verapamil, and many other drugs. - Is digoxin safe in pregnancy?
It may be used if necessary, but it requires close monitoring to avoid maternal and foetal toxicity. - What should I do if I miss a dose of digoxin?
Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up. - Can digoxin cause kidney damage?
No, but poor kidney function can lead to digoxin accumulation and toxicity. - Can digoxin cause weight gain?
No, weight gain is not a direct side effect. However, worsening heart failure can cause fluid retention and weight gain. - What foods should I avoid while taking digoxin?
Avoid high-fibre meals around dosing times, as they can reduce absorption. - How long does digoxin take to work?
Improvement in heart rate may be seen within hours, but full benefits for heart failure may take weeks. - How should digoxin be stored?
Store at room temperature, away from light and moisture.