Drug Information: Digoxin
Digoxin is a cardiac glycoside medication derived from the foxglove plant. It’s primarily used to treat heart failure and certain types of irregular heartbeats, particularly atrial fibrillation. Digoxin works by increasing the force of heart muscle contractions and slowing down the heart rate. Careful monitoring is essential due to its narrow therapeutic window, meaning the difference between a therapeutic dose and a toxic dose is small. It’s important to be aware of potential drug interactions and to monitor potassium levels, as hypokalemia can increase the risk of Digoxin toxicity.
Category
Antiarrhythmic
Mechanism of Action
Digoxin’s mechanism of action is multifaceted, primarily involving the inhibition of the Na+/K+-ATPase pump in cardiac myocytes. This inhibition leads to an increase in intracellular sodium concentration. The increased intracellular sodium reduces the activity of the Na+/Ca2+ exchanger, which normally removes calcium from the cell in exchange for sodium. As a result, intracellular calcium concentration increases. This elevated calcium level enhances the force of myocardial contraction (positive inotropic effect). In addition to its direct effect on cardiac myocytes, Digoxin also increases vagal tone. This parasympathomimetic effect slows the conduction of electrical impulses through the atrioventricular (AV) node, reducing the ventricular rate in supraventricular tachyarrhythmias like atrial fibrillation and atrial flutter. The increased vagal tone also contributes to its negative chronotropic effect (slowing heart rate).
Clinical Uses
Digoxin is primarily used in the management of heart failure, particularly in patients with reduced ejection fraction. Its positive inotropic effect helps to increase cardiac output and improve symptoms. It’s also commonly used to control the ventricular rate in atrial fibrillation and atrial flutter. By slowing AV conduction, Digoxin helps to prevent rapid ventricular rates, which can lead to hemodynamic instability. While other medications are often preferred for rate control, Digoxin remains a valuable option, especially in patients with heart failure or when other medications are contraindicated. Digoxin has also been used in the past for supraventricular tachycardia, although other treatments are often more effective and preferred now.
Dosage
Digoxin dosage varies widely based on individual patient factors, including age, renal function, and the specific condition being treated. It can be administered orally or intravenously.
**Adults:**
* **Oral Loading Dose:** Typically not used anymore.
* **Oral Maintenance Dose:** 0.125 mg to 0.25 mg daily. Dosage adjustments are crucial based on renal function and serum Digoxin levels.
* **IV Loading Dose:** Typically not used anymore.
* **IV Maintenance Dose:** Varies depending on the condition and patient, usually lower than oral dose.
**Pediatrics:** Dosing is weight-based and requires careful calculation by a qualified healthcare professional. Consult pediatric-specific dosing guidelines.
* It is important to monitor drug levels and ensure patient is not developing toxicity.
Indications
Common indications for Digoxin include:
* Heart Failure (especially with reduced ejection fraction)
* Atrial Fibrillation (for rate control)
* Atrial Flutter (for rate control)
* Supraventricular Tachycardia (less commonly used now)
Contraindications
Digoxin is contraindicated in patients with:
* Ventricular fibrillation
* Ventricular tachycardia (unless due to heart failure)
* Hypersensitivity to Digoxin
* AV block (second or third degree) in the absence of a pacemaker
* Wolff-Parkinson-White syndrome with atrial fibrillation (risk of rapid ventricular conduction)
* Severe renal impairment (requires careful dose adjustment)
* Hypertrophic obstructive cardiomyopathy (HOCM) unless used to treat atrial fibrillation
FAQ
**Q: What are the common side effects of Digoxin?**
A: Common side effects include nausea, vomiting, diarrhea, loss of appetite, visual disturbances (blurred vision, yellow halos), and fatigue. More serious side effects include arrhythmias, bradycardia, and neurological symptoms.
**Q: What is Digoxin toxicity?**
A: Digoxin toxicity occurs when the level of Digoxin in the blood is too high. This can lead to serious cardiac arrhythmias and other life-threatening complications. Symptoms include nausea, vomiting, confusion, visual disturbances, and irregular heartbeats.
**Q: How is Digoxin toxicity treated?**
A: Treatment for Digoxin toxicity may include stopping the medication, administering potassium (if potassium levels are low), and in severe cases, administering Digoxin-specific antibody fragments (Digibind or DigiFab).
**Q: What medications can interact with Digoxin?**
A: Many medications can interact with Digoxin, including amiodarone, quinidine, verapamil, diltiazem, and some antibiotics. These medications can increase Digoxin levels in the blood, increasing the risk of toxicity.
**Q: How often should Digoxin levels be monitored?**
A: Digoxin levels should be monitored regularly, especially when starting the medication, after dose changes, or when interacting medications are added or removed.
**Q: Can Digoxin be used during pregnancy?**
A: Digoxin can be used during pregnancy if clinically necessary, but the benefits and risks should be carefully weighed. Fetal monitoring may be required.
**Q: What should I do if I miss a dose of Digoxin?**
A: If you miss a dose of Digoxin, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up.
**Q: Does Digoxin cure heart failure?**
A: No, Digoxin does not cure heart failure. It helps manage the symptoms and improve the quality of life for people living with heart failure.
“`