Digoxin

What is this medication for?

• CHF with atrial fibrillation / supraventricular tachyarrhythmias — drug of choice for the arrhythmia component; adjunct (with diuretics ± ACE inhibitor) in DCM
• Dilated cardiomyopathy, advanced AV valve insufficiency; relatively contraindicated in hypertrophic cardiomyopathy

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Acute into a vein toxic dose in dogs reported at 0.177 mg/kg. Toxicity management: stop drug, correct electrolytes/acid-base, continuous ECG; lidocaine or phenytoin for life-threatening arrhythmias; atropine for bradyarrhythmias; digoxin immune Fab (digibind) for life-threatening toxicity (expensive, rare veterinary use); repeated activated charcoal (enterohepatic recirculation).

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• stomach/intestinal: loss of appetite, mild upset, weight loss, diarrhea (Usually first extracardiac signs)
• Vomiting after into a vein dosing (Expected, not alarming)

Worth a phone call to your veterinarian

• Any arrhythmia (AV block, bigeminy, ST changes, paroxysmal unusually fast heart rate with block, multifocal VPCs) (Toxic-range levels; can mimic worsening heart disease)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Ventricular fibrillation; digitalis intoxication; feline HCM (relatively — ↑ myocardial O₂ demand, dynamic outflow obstruction)
• has or has had: Glomerulonephritis + heart failure; idiopathic hypertrophic subaortic stenosis
• has or has had: Severe pulmonary disease/hypoxia, acute myocarditis, acute MI, frequent VPCs/V-tach, constrictive pericarditis, incomplete AV block; renal disease (monitor levels); electrolyte/acid-base disturbances (hypoK, hyperCa ↑ toxicity)
• has or has had: MDR1/ABCB1 mutant dogs: WSU does NOT recommend dose reduction — but do therapeutic drug monitoring

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Hypokalemia-causing drugs (diuretics)
  • Quinidine, amiodarone, verapamil, spironolactone & many others
  • Anticholinergic antiarrhythmics (quinidine, procainamide, disopyramide)
  • P-glycoprotein inhibitors

Storage and handling

Room temperature; light-resistant container. Elixir vs tablet affects absorption — don't switch forms without re-titration.

Good to know

• Pimobendan has largely replaced digoxin as first-line inotrope — digoxin's remaining niche is rate control of atrial fibrillation and adjunctive DCM therapy.
• Acute into a vein toxic dose in dogs reported at 0.177 mg/kg. Toxicity management: stop drug, correct electrolytes/acid-base, continuous ECG; lidocaine or phenytoin for life-threatening arrhythmias; atropine for bradyarrhythmias; digoxin immune Fab (digibind) for life-threatening toxicity (expensive, rare veterinary use); repeated activated charcoal (enterohepatic recirculation).
• Postpone elective cardioversion until digoxin withheld 1–2 days.