Spironolactone: Uses and Benefits for Cats and Dogs

1 Spironolactone for Cats and Dogs

Spironolactone is a diuretic with a special mechanism; it blocks the hormone aldosterone, which is released heavily in heart failure and some conditions like Conn’s syndrome.

Aldosterone’s main job is to retain sodium and excrete potassium in the kidneys.

Spironolactone blocks this, increasing sodium in urine while retaining potassium – earning it the name ‘potassium-sparing diuretic.’

More sodium out means more water out, increasing urine and the diuretic effect. Overall the diuresis is mild.

Spironolactone also blocks aldosterone’s effect on heart muscle; high aldosterone is toxic to the heart.

Spironolactone is prescription-only, obtained from or via a vet.

The US FDA hasn’t approved it for animals, but vets may prescribe it extra-label.

Spironolactone formulations

This drug is registered for human use only.

Human: Aldactone® (Searle) and generics.

Veterinary: none currently.

Uses in cats and dogs

1. Reduces fluid buildup in conditions like heart failure; also treats ascites from some liver diseases.

2. Helps control hypertension in cats.

Precautions and side effects

1. Vet-prescribed spironolactone is generally safe and effective, but can cause side effects in some animals.

2. Don’t use in animals known allergic to it.

3. Avoid in animals with kidney damage, liver disease, Addison’s disease, or high blood potassium.

4. Side effects are rare and usually mild; they fade once stopped.

5. It may interact with other drugs. Ask your vet whether your pet’s other meds interact – including aspirin, enalapril, digoxin, and other diuretics.

6. Side effects include dehydration, low sodium, high potassium, drowsiness, anorexia, vomiting, diarrhea. Facial dermatitis is documented in cats, more likely in those also on ACE inhibitors like enalapril or benazepril.

Spironolactone strengths

Tablets of 25 mg, 50 mg, and 100 mg.

Dosage

Note: always consult a vet before dosing.

1. For dogs and cats, 0.25-2 mg per pound (0.5-4 mg/kg), once or twice daily.

2. Duration depends on the condition and response. Even if the pet seems recovered, finish the full course unless the vet says otherwise.