# Spironolactone: veterinary dose and monograph

> Spironolactone is a veterinary diuretic. Potassium-sparing aldosterone-receptor antagonist — a weak diuretic whose real value in heart failure is blocking aldosterone-driven cardiac / vascular remodelling. Indications include adjunct in congestive heart failure (aldosterone blockade); refractory ascites (hepatic / right-sided CHF); hyperaldosteronism (feline, off-label). This monograph lists 3 reference doses for dogs, cats and rabbits, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/spironolactone · Last reviewed: 2026-10-01

## 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

*Spironolactone doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| CHF adjunct / ascites | 1–2 mg/kg | PO | q12–24h with food | — |

- 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

*Spironolactone doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| CHF / hyperaldosteronism (off-label) | 1–2 mg/kg | PO | q12–24h | — |

- 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

*Spironolactone doses for rabbits*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| CHF adjunct (potassium-sparing diuretic) | 1–2 mg/kg | PO | q12h | — |

- 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

> **Caution:** 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](https://vetmasterji.com/drugs/acetazolamide)
- [Furosemide](https://vetmasterji.com/drugs/furosemide)
- [Hydrochlorothiazide](https://vetmasterji.com/drugs/hydrochlorothiazide)
- [Mannitol](https://vetmasterji.com/drugs/mannitol)
- [Torsemide (Torasemide)](https://vetmasterji.com/drugs/torsemide)

## Frequently asked questions

### What is the dose of Spironolactone for dogs?

Reference doses for Spironolactone in dogs: 1–2 mg/kg PO q12–24h with food (CHF adjunct / ascites). Confirm against the label and the patient before use.

### What is the dose of Spironolactone for cats?

Reference doses for Spironolactone in cats: 1–2 mg/kg PO q12–24h (CHF / hyperaldosteronism (off-label)). Confirm against the label and the patient before use.

### What is the dose of Spironolactone for rabbits?

Reference doses for Spironolactone in rabbits: 1–2 mg/kg PO q12h (CHF adjunct (potassium-sparing diuretic)). Confirm against the label and the patient before use.

### When should Spironolactone not be used?

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

### What are the side effects of Spironolactone in animals?

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

## Sources

- Plumb's Veterinary Drug Handbook
- Papich, Papich Handbook of Veterinary Drugs, 5th edition
- Carpenter, Exotic Animal Formulary

---

VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.