Furosemide: veterinary dose and monograph

At a glance

Drug class

Diuretic

Also known as

Lasix, Salix

Species with doses

Dogs, Cats, Cattle, Horses, Rabbits, Ferrets, Guinea pigs, Chinchillas, Hamsters, Rats, Mice, Gerbils, Hedgehogs, Sugar gliders and Primates

General dose range

1–4 mg/kg IV q8–12h — check the species tables for the indication

Routes

IV, PO, IM, SC

Last reviewed

1 October 2026

Indications

• Congestive heart failure / pulmonary oedema
• Hypercalciuric nephropathy
• Adjunctive hyperkalaemia management
• Antihypertensive (occasional)
• Bovine post-partum udder oedema
• Equine exercise-induced pulmonary haemorrhage (EIPH)

Furosemide 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

• Acute pulmonary oedema (CHF crisis): Papich 5e: 2 mg/kg IV, then 2 mg/kg every 30 min until improvement. Plumb’s p.559 (Kittleson): up to 8 mg/kg IV or IM every 1–2 h until the respiratory rate/character improves; 1–4 mg/kg IV, IM or PO q1–12h (Rozanski). Reduce once breathing improves; convert to oral maintenance; monitor electrolytes and renal values.
• CHF maintenance: Papich 5e: commonly 2 mg/kg PO q12h initially, then 1–2 mg/kg q12h (range 2–6 mg/kg q8–12h). Plumb’s p.559: from 1 mg/kg every other day (mild) to 4 mg/kg q8h (severe) (Kittleson); most dogs need <2 mg/kg q12h — use the lowest effective dose and recheck renal values 5–10 days after starting (Rush).
• Acute pulmonary oedema / oliguric AKI — CRI: Papich 5e: 0.66 mg/kg IV bolus then 0.66 mg/kg/h for 8 h. Plumb’s p.559: 0.66 mg/kg/h may give more diuresis with less kaliuresis (Kittleson); oliguric AKI 0.1–1 mg/kg/h after a successful bolus (Silverstein). Monitor fluid balance closely.

Cats

• Acute pulmonary oedema: Plumb’s p.559 (Kittleson): cats initially 2–4 mg/kg IV or IM (IV acts in ~5 min vs ~30 min IM); may repeat within 1–2 h, then reduce sharply once the respiratory rate falls to avoid severe dehydration. Papich 5e: start with 1 mg/kg and increase as needed within 1–4 mg/kg.
• CHF maintenance: Papich 5e: 1–4 mg/kg q8–24h IV, IM, SC or PO, starting at 1 mg/kg. Plumb’s p.559: chronic therapy often 6.25 mg per cat once daily (range 6.25 mg q48h to 12.5 mg q8h); use the lowest dose that controls signs and have owners log sleeping respiratory rate. Typical feline maintenance is 1–2 mg/kg PO q12–24h (≈6.25 mg per cat daily).

Cattle

• Post-partum udder oedema (label): Plumb’s p.560 (Lasix label) and Papich 5e: 500 mg per cow once daily, OR 250 mg twice daily, IM or IV (2 g PO once daily also labelled). Do not continue beyond 48 h post-partum.
• Diuresis (weight-based): Plumb’s p.560 (Howard 1986): 2.2–4.4 mg/kg IV q12h. Observe milk/meat withdrawal for the product used.

Horses

• EIPH prophylaxis: Papich 5e: 0.5 or 1 mg/kg IV 4 h before exercise (or 24 h pre-race) — check local racing rules. Horses should have water available.
• Congestive heart failure / oedema: Plumb’s p.560 (Mogg 1999): initially 1–2 mg/kg IM or IV q6–12h; long-term 0.5–2 mg/kg PO or IM q8–12h. Papich 5e: 1 mg/kg q8h IM/IV (or 250–500 mg/horse q6–8h); CRI 0.12 mg/kg IV then 0.12 mg/kg/h.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Post-partum udder oedema (label): Plumb’s p.560 (Lasix label) and Papich 5e: 500 mg per cow once daily, OR 250 mg twice daily, IM or IV (2 g PO once daily also labelled). Do not continue beyond 48 h post-partum.
• Diuresis (weight-based): Plumb’s p.560 (Howard 1986): 2.2–4.4 mg/kg IV q12h. Observe milk/meat withdrawal for the product used.

Rabbits

• CHF / pulmonary oedema: Plumb's p.560 (Ivey & Morrisey 2000): rabbits — CHF 2–5 mg/kg PO/SC/IM/IV q12h; acute pulmonary oedema 1–4 mg/kg IV or IM q4–6h.

Ferrets

• CHF: Plumb's p.560: fulminant CHF 2–3 mg/kg IM or IV, then 1–2 mg/kg PO q12h maintenance (Hoeffer 2000); or 1–4 mg/kg PO/SC/IM/IV 2–3×/day (Williams 2000).

Guinea pigs

• Diuresis / oedema: Plumb's p.560: 5–10 mg/kg q12h.

Chinchillas

• Diuresis / oedema: Plumb's p.560 (Adamcak & Otten 2000): Mice/Rats/Gerbils/Hamsters/Guinea pigs/Chinchillas 5–10 mg/kg q12h.

Hamsters

• Diuresis / oedema: Plumb's p.560: 5–10 mg/kg q12h.

Rats

• Diuresis / oedema: Plumb's p.560: 5–10 mg/kg q12h.

Mice

• Diuresis / oedema: Plumb's p.560: 5–10 mg/kg q12h.

Gerbils

• Diuresis / oedema: Plumb's p.560: 5–10 mg/kg q12h.

Hedgehogs

• Oedema / congestive heart failure: Carpenter Exotic Animal Formulary 6th ed, Table 8-7 (p.519): hedgehogs 2.5–5 mg/kg PO/SC/IM q8h; 3–5 mg/kg SC/IM q6–8h for congestive heart failure.

Sugar gliders

• Diuresis / oedema: Carpenter Exotic Animal Formulary 6th ed, Table 7-5 (p.501): sugar gliders 1–5 mg/kg PO/SC/IM q6–12h; 2–4 mg/kg PO/SC/IM.

Primates

• CHF / pulmonary oedema (monkeys): Carpenter Exotic Animal Formulary 6th ed, Table 13-7 (p.707): monkeys 1–4 mg/kg IV or 2–4 mg/kg IM q8h; chimpanzees 1–2 mg/kg PO/IM/IV; common marmosets 1–4 mg/kg PO/SC q12h.

Contraindications

Anuria. Hypersensitivity (sulfonamide cross-reactivity possible). Discontinue if azotaemia/oliguria worsens. Caution in hepatic dysfunction (may precipitate hepatic coma), diabetes, electrolyte/water imbalance.

Species-specific warnings

Cats: Highly sensitive — start at lower dose (1 mg/kg). Risk of severe dehydration and hypotension. Monitor BUN, creatinine, K⁺ closely.

Dogs: Use lowest effective dose for chronic CHF. Watch for hypokalaemia, azotaemia in older dogs with comorbid CKD.

Horses: Used pre-race for EIPH at 250–500 mg IV 4 h before exercise. BANNED on race day in some jurisdictions (US: regulated, UK: prohibited day-of-race). No food-animal residue concern.

Cattle: Used post-calving for udder oedema at 250–500 mg IM/IV. Limited food-animal residue data — extra-label, follow FARAD guidance.

Goats: Goats handle furosemide similarly to cattle — same dose range (0.5–1 mg/kg IV/IM).

Adverse effects

• Hyponatraemia, hypokalaemia, hypomagnesaemia, hypocalcaemia
• Pre-renal azotaemia (with dehydration)
• Ototoxicity (cats, high-dose IV; dogs >22 mg/kg IV)
• GI upset
• Anaemia, leukopenia (rare)

Drug interactions

• Aminoglycosides (gentamicin, amikacin): synergistic ototoxicity and nephrotoxicity
• NSAIDs (meloxicam, carprofen): reduced diuretic effect (PG blockade) + additive renal risk
• ACE inhibitors (enalapril, benazepril): additive hypotension; "first-dose hypotension" caution
• Digoxin: furosemide-induced hypokalaemia potentiates digoxin toxicity (arrhythmias)
• Corticosteroids: additive hypokalaemia
• Insulin: reduced glucose tolerance — monitor diabetic patients
• Lithium: decreased clearance — toxicity risk (uncommon in vet practice)
• Probenecid: decreases furosemide effect

Pregnancy and lactation

Use only when benefit outweighs risk. Crosses placenta. Excreted in milk in low concentrations. May suppress lactation by reducing maternal hydration. Used in CHF management throughout pregnancy when needed. FDA Category C (human).

Monitoring

• Renal function (BUN, creatinine) — baseline and within 7 days of dose change, then quarterly
• Electrolytes (K⁺, Na⁺, Cl⁻, Mg²⁺) — baseline and at 5–7 days, then every 3 months
• Hydration / body weight / appetite — daily during initial titration
• Blood pressure if on ACE-I — first-dose hypotension risk
• CHF-specific: respiratory rate at rest (target <30/min), exercise tolerance, abdominal distension
• Auscultation for crackles / oedema response

Toxicity and overdose

Acute overdose: severe dehydration, hypovolaemia, hypotension, syncope. Electrolyte derangement: hypokalaemia (weakness, arrhythmias), hyponatraemia, hypochloraemia, metabolic alkalosis. Ototoxicity at very high IV doses (>2 mg/kg, especially rapid infusion or with aminoglycoside). Pre-renal azotaemia from volume depletion. Cats: very sensitive — start at lower end of dose range.

Management: Stop drug. Aggressive IV fluid resuscitation with balanced crystalloid (lactated Ringer's) to restore volume. Electrolyte correction: K⁺ supplementation (KCl 0.05–0.1 mEq/kg/h IV — never bolus), Mg supplementation if low. Monitor blood pressure, urine output, electrolytes, renal function. Anti-arrhythmic if needed. Ototoxicity: usually reversible once drug discontinued but may be permanent at very high doses.

Clinical pearls

• Acute pulmonary oedema (CHF crisis): 2–8 mg/kg IV bolus dogs, 1–2 mg/kg IV cats — repeat in 30–60 min if no improvement
• CRI (continuous rate infusion) 0.66–1 mg/kg/h often more effective and gentler than repeated boluses in refractory CHF
• Chronic CHF maintenance: lowest dose that controls signs — typically 1–4 mg/kg PO q12–24h in dogs
• Cats: more sensitive — start 1 mg/kg PO q12h and titrate carefully
• Combine with spironolactone (1–2 mg/kg PO q12h) for K⁺-sparing benefit in chronic dosing
• Race horses: "Lasix" 250–500 mg IV 4 h pre-race to prevent EIPH — banned in some jurisdictions
• Avoid IM injection in cats — irritating; SC or IV preferred

Mechanism of action

Loop diuretic. Inhibits the Na⁺/K⁺/2Cl⁻ co-transporter (NKCC2) on the luminal side of the thick ascending limb of Henle, blocking reabsorption of sodium, chloride, potassium, calcium, and magnesium. Produces rapid, dose-dependent diuresis with significant electrolyte loss. Also has a direct venodilator effect via prostaglandin release — preload reduction is partly independent of diuresis, useful in acute pulmonary oedema.

Formulations and products

• Injection 50 mg/mL
• Tablet 12.5 mg
• Tablet 50 mg
• Zubion F (Intas (Neovet)) — Furosemide 55 mg + Buparvaquone 50 mg / mL (oil base), Combination injection (oily base) — for bovine theileriosis with pulmonary oedema

Storage

Tablets: 15–30 °C, dry, protected from light. Oral solution: 15–30 °C, protected from light. Injection: 15–30 °C — DO NOT refrigerate (crystallisation). Discard if discoloured (yellow → brown).

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
• Hydrochlorothiazide
• Mannitol
• Spironolactone
• Torsemide (Torasemide)

Frequently asked questions