Digoxin Mnemonic Lecture Notes

Introduction

• Host: Medicosis Perfectionatus
• Topic: Digoxin and its uses in medicine.

What is Digoxin?

• Class: Cardiac glycosides (also known as digitalis).
• Members of digitalis:
  • Digoxin
  • Digitoxin
  • Wabain

Uses of Digoxin

1. Boost Cardiac Contractility
   • Important for patients with congestive heart failure (CHF).
   • Helps the heart pump harder.
2. Increase Refractory Period at the Atrioventricular (AV) Node
   • Delays conduction in the AV node, lowering heart rate.
   • Useful for patients with palpitations or tachyarrhythmias (e.g., supraventricular tachycardia).

Types of Heart Failure

• Two types:
  • Systolic Failure (heart fails to contract)
  • Diastolic Failure (heart fails to fill properly)
• Digoxin is used in systolic failure.

Supraventricular Arrhythmias

• Can use digoxin for:
  • Atrial fibrillation
  • Atrial flutter
  • Paroxysmal supraventricular tachycardia
• Contraindicated in Wolff-Parkinson-White (WPW) Syndrome
  • WPW involves an accessory pathway that bypasses the normal conduction path, leading to tachyarrhythmia.
  • Digoxin slows the AV node, worsening WPW.

Drugs Contraindicated in WPW Syndrome

• 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 decreases sodium entry, affecting conduction velocity and increasing risk of re-entrant arrhythmias.

Mechanism of Action of Digoxin

• Inhibits sodium-potassium ATPase pump.
  • Leads to sodium accumulation inside the cardiac myocyte.
  • Impairs calcium extrusion, increasing intracellular calcium levels, boosting contractility (calcium-induced calcium release).

Digoxin Mnemonic

• All members (digoxin, digitalis, digitoxin) have the letter "D".
• Mechanism Recap:
  • Destroys sodium-potassium ATPase, leading to increased contractility and delayed AV conduction.

Important Points

• Dosing: Requires a loading dose, large volume of distribution, and is displaceable by other drugs.
• Onset: Slow, not suitable for acute heart failure; use dobutamine instead.
• Mortality: Does not lower mortality in CHF or myocardial infarction (MI); improves symptoms but not longevity.
• Toxicity: Narrow therapeutic window with low safety margin; side effects include disorientation, visual disturbances, and yellow-green halos.

EKG Changes

• Can depress ST segment and decrease QT interval.

Digoxin Toxicity Management

• Antidote: DigiBind (anti-digoxin antibodies).
• Only use digoxin in CHF with decreased ejection fraction, not preserved ejection fraction.

Summary of Key Points

• Digoxin Effects:
  • Destroys sodium-potassium ATPase
  • Increases contractility
  • Delays AV conduction (lowers heart rate)
• Caution: Not for use in WPW or acute heart failure.

Conclusion

• Lecture promotes additional courses available for further learning on cardiac pharmacology and antidotes.
• Discount code: TOXIDROME for 40% off courses.
• Host encourages subscriptions and engagement with content.