Digoxin

General

• Type: Cardiac glycoside
• Dosage Forms: PO, IV, IM
• Common Trade Names: Digitek, Digox, Lanoxin (US)

Adult Dosing

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

Special Populations

• Pregnancy Rating:
• 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: N/V, diarrhea, abd pain
• CV: Bradycardia, SA/AV block, ventr arrhythmias

Pharmacology

• Half-life:
• Metabolism:
• Excretion:
• Kinetics
  • Onset of action = 1.5-4hr (IV)

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

See Also

• Digoxin Toxicity
• Antiarrhythmics