Spironolactone: veterinary dose and monograph

At a glance

Drug class

Diuretic

Also known as

Aldactone, Prilactone

Species with doses

Dogs, Cats and Rabbits

General dose range

1–2 mg/kg PO q12–24h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Adjunct in congestive heart failure (aldosterone blockade)
• Refractory ascites (hepatic / right-sided CHF)
• Hyperaldosteronism (feline, off-label)

Spironolactone dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• CHF adjunct / ascites: Papich 5e: 2–4 mg/kg/day (or 1–2 mg/kg q12h) PO — start 2 mg/kg/day, not above 4 mg/kg/day; European label 2 mg/kg/day. Plumb’s p.1075: refractory CHF 1–2 mg/kg PO q12h (Ware & Keene 2000); with other diuretics when hypokalaemic 2–4 mg/kg once daily; hypertension 1–2 mg/kg q12h. Monitor potassium and renal values.

Cats

• CHF / hyperaldosteronism (off-label): Plumb’s p.1075: refractory CHF or hypertension 1–2 mg/kg PO q12h (Ware & Keene; Stepian); primary hyperaldosteronism 1–2 mg/kg twice daily (Caney 2009). Papich 5e: use in cats is controversial — can cause facial dermatitis and efficacy is questionable; 2–4 mg/kg/day has been used.

Rabbits

• CHF adjunct (potassium-sparing diuretic): Carpenter's 6th ed (Rabbit cardiovascular table): 1–2 mg/kg PO q12h.

Contraindications

Hyperkalaemia, hypoadrenocorticism, significant renal failure. Caution combining with ACE inhibitors / ARBs / potassium supplements (additive hyperkalaemia). Pregnancy.

Adverse effects

• Hyperkalaemia (especially with RAAS blockers)
• GI upset
• Facial dermatitis / excoriation reported in some cats

Drug interactions

• ACE inhibitors / ARBs (telmisartan) / potassium supplements: additive HYPERKALAEMIA — monitor potassium
• NSAIDs: reduce the diuretic effect and add renal risk
• Digoxin: spironolactone can raise serum digoxin levels

Pregnancy and lactation

Avoid in pregnancy — anti-androgenic activity can feminise male foetuses.

Monitoring

• Serum potassium and renal values — particularly when combined with an ACE inhibitor / ARB
• Bodyweight / abdominal girth when treating ascites

Toxicity and overdose

Overdose risk is hyperkalaemia (arrhythmia, weakness) with dehydration / hyponatraemia; the danger is amplified by concurrent RAAS blockade or renal impairment.

Clinical pearls

• Its benefit in heart failure is anti-remodelling, not its modest diuresis — think of it as a neurohormonal blocker
• Watch potassium closely when stacked on top of an ACE inhibitor or telmisartan
• Give with food and warn cat owners about the occasional facial dermatitis reaction

Mechanism of action

Competitive aldosterone (mineralocorticoid)-receptor antagonist in the distal nephron — promotes sodium / water excretion while retaining potassium (a weak diuretic). Its principal cardiac benefit is blocking aldosterone-mediated myocardial and vascular fibrosis and remodelling.

Formulations and products

• Prilactone 10 mg / 40 mg / 80 mg tablet (canine)
• Spironolactone 25 mg tablet
• Prilactone (Ceva) — 10 / 40 / 80 mg, Tablet
• Cardalis (Ceva) — Spironolactone + benazepril, Chewable tablet
• Aldactone — 25 / 50 / 100 mg, Tablet (human-label)

Storage

Store at 15–25 °C, dry.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other diuretics

• Acetazolamide
• Furosemide
• Hydrochlorothiazide
• Mannitol
• Torsemide (Torasemide)

Frequently asked questions