Lecture Notes: Digoxin Mnemonic and Pharmacology

Introduction

• Speaker: Medicosis Perfectionatus
• Topic: Digoxin and its pharmacological uses
• Class: Cardiac Glycosides (Digitalis)

Cardiac Glycosides

Subtypes

1. Digoxin
2. Digitoxin
3. Wabain

Reasons for Digoxin Use

• Boost Cardiac Contractility
  • Important for congestive heart failure (CHF) patients.
• Increase Refractory Period at AV Node
  • Delays conduction, lowers heart rate.
  • Useful for arrhythmias (e.g., supraventricular tachycardia).

Types of Heart Failure

• Systolic Failure
  • Heart fails to contract; digoxin is effective here.
• Diastolic Failure
  • Not suitable for digoxin use.

Supraventricular Arrhythmias Indications

• Can Use Digoxin For:
  • Atrial Fibrillation
  • Atrial Flutter
  • Paroxysmal Supraventricular Tachycardia
• Do Not Use Digoxin For:
  • Wolff-Parkinson-White (WPW) Syndrome
    • Explanation: WPW bypasses normal conduction pathways, making digoxin's action counterproductive.

Drugs Contraindicated in WPW

• A: Adenosine
• B: Beta Blockers
• C: Calcium Channel Blockers
• D: Digoxin

Action Potential in Ventricular Muscles

• Phases of Action Potential
  • Phase 0: Rapid sodium influx
  • Digoxin slows down this process, decreasing conduction velocity
  • Risk of re-entrant arrhythmias if conduction velocity decreases too much

Mechanism of Action of Digoxin

• Inhibition of Na+/K+ ATPase
  • Sodium accumulates inside the cell
  • Decreased calcium extrusion leads to increased intracellular calcium
  • Result: Increased cardiac contractility due to calcium-induced calcium release

Summary of Digoxin Effects

• Increases Contractility
• Delays AV Conduction
• Decreases Heart Rate
• Does Not Lower Mortality in CHF or MI patients
• Toxicity Symptoms:
  • Disorientation
  • Visual disturbances (yellow-green halos)
  • ST segment depression and decreased QT interval on EKG

Treatment of Digoxin Toxicity

• Antidote: DigiBind
  • Binds to digoxin, decreasing toxicity until elimination

Indications for Digoxin Usage

• Indicated For:
  • CHF with decreased ejection fraction (systolic failure)
• Not Indicated For:
  • Preserved ejection fraction

Key Takeaways

• Digoxin effects summarized:
  • Destroys Na+/K+ ATPase
  • Increases contractility
  • Delays AV conduction, decreases heart rate
  • No impact on mortality or longevity

Resources

• Medicosis's cardiac pharmacology course covers digoxin and related medications.
• Discount code available for courses: TOXIDROME

Conclusion

• Encouragement to subscribe and support Medicosis Perfectionatus.