Digoxin

General

• Type: Cardiac glycoside; CHF medications
• Mechanism of action- Inhibits Na+/K+ ATPase, leading to an increase in intracellular sodium that can increase cardiac contractility
• Dosage Forms: PO, IV, IM
• Common Trade Names: Digitek, Digox, Lanoxin

Adult Dosing

• Loading dose = 0.25mg IV q2hr until effect (max total = 1.5mg)
• in acute atrial fibrillation with RVR with heart failure = 0.5mg IV, then 0.25mg IV q4hr until effect or max 1.5mg

Special Populations

• Pregnancy Rating: C
• Lactation risk:
• Renal Dosing
  • Adult
  • Pediatric
• Hepatic Dosing
  • Adult
  • Pediatric

Indications

• RVR control in a-fib/flutter, PSVT

Contraindications

• Allergy to class/drug
• WPW
  • Increases conduction velocity in atrial tissue

Adverse Reactions

Digoxin toxicity

• GI: nausea and vomiting, diarrhea, abdominal pain
• CV: Bradycardia, SA/AV block, ventr arrhythmias
• Neuro: altered mental status, visual disturbances (yellow-tinted vision)

Pharmacology

• Onset of action
  • IV = 5-30 minutes
  • PO = 0.5-2 hours
• Half-life: 36-48 hours (may be increased with renal impairment)
• Absorption: 60-80% absorption after oral administration
• Metabolism: ~16% is converted to metabolites
• Excretion: Almost entirely by the kidneys

Mechanism of Action

• Inhibits Na+/K+ ATPase in the myocardium
  • Causes increase in intracellular sodium levels
  • Results in reversal of sodium-calcium exchanger
    • Normally imports three extracellular sodium ions into the cardiac myocyte in exchange for one intracellular calcium being exported
  • Sodium accumulates intracellularly and is exchanged for Calcium.
  • Causes an increase in the intracellular calcium concentration increasing contractility
    • Also a lengthening of phase 4 and phase 0 of the cardiac action potential which ultimately decreases heart rate
• Summary
  • Inhibits NaK pump
    • Positive inotropy
  • Negative chronotropy/dromotropy
    • Indirect vagal stimulator

Indications by Condition

The following table is automatically generated from disease/condition pages across WikEM.

Indication	Dose	Context	Route	Population
Atrial fibrillation (main)	500 mcg IV, then 250 mcg q4h x2 (total 1000 mcg digitizing dose)	Rate control (if hypotensive or advanced HF)	IV	Adult

See Also

• Digoxin Toxicity
• Antiarrhythmics