Amphotericin B: veterinary dose and monograph

At a glance

Drug class

Antifungal

Also known as

Fungizone, AmBisome (liposomal), Amphotret

Species with doses

Dogs, Cats and Horses

General dose range

0.25–0.5 mg/kg IV 2–3× per week (cumulative-dose based) — check the species tables for the indication

Routes

IV, SC

Last reviewed

1 October 2026

Indications

• Severe systemic mycoses — blastomycosis, histoplasmosis, cryptococcosis, coccidioidomycosis, disseminated candidiasis
• Refractory fungal infection not controlled by azoles
• Leishmaniasis (lipid formulations)
• Induction therapy in critically ill fungal patients (then step down to an azole)

Amphotericin B 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

• Systemic mycosis (conventional, to cumulative dose): Papich 5e: conventional (deoxycholate) 0.5 mg/kg IV slowly every 48 h to a cumulative 4–8 mg/kg; leishmaniasis 0.5 mg/kg on alternate days for 4 weeks (WHO discourages this use). Saline diuresis before and after; monitor BUN/creatinine before each dose and stop if azotaemia rises.
• Lipid/liposomal formulation: Papich 5e: first dose 0.5 mg/kg, then 1–3 mg/kg/day if tolerated, infused over 60–120 min, three times weekly or every other day for up to 9–12 treatments (cumulative target 12–36 mg/kg, though many dogs switch to an oral azole first). Monitor renal values.
• Subcutaneous protocol (conventional): Papich 5e: 0.5–0.8 mg/kg diluted in 500 mL (dogs under 20 kg) or 1000 mL (over 20 kg) of 0.45% saline with 2.5% dextrose, not above 20 mg/L, given SC two or three times weekly. Sterile abscesses at the injection site are an important complication.

Cats

• Systemic mycosis (cautious): Papich 5e: cats have received regimens similar to dogs (e.g. 0.25 mg/kg of the conventional formulation) — many clinicians start lower. Strict renal monitoring.
• Liposomal formulation: Papich 5e: liposomal amphotericin 1 mg/kg IV three times weekly for up to 12 treatments. Monitor renal values.

Horses

• Systemic mycosis: Papich 5e: 0.3 mg/kg IV on day 1 and the following 3 days, then repeat after a 24–48 h drug-free interval. Cost limits use in horses; monitor renal function.

Contraindications

Pre-existing renal impairment (relative — use lipid formulation, reduce dose). Dehydration (must volume-load first). Concurrent nephrotoxins. Rapid IV bolus (cardiotoxicity). Known hypersensitivity. Never give by routes other than slow IV (for systemic disease).

Species-specific warnings

Cats: Cats are particularly sensitive to amphotericin nephrotoxicity — use lower per-dose amounts, prefer lipid formulations, and monitor renal values rigorously.

Adverse effects

• Nephrotoxicity (azotaemia, tubular damage, hypokalaemia, hypomagnesaemia) — dose-limiting
• Infusion reactions: fever, vomiting, tremor, phlebitis
• Anaemia (reduced erythropoietin)
• Cardiotoxicity/arrhythmia with rapid infusion
• Hypokalaemia

Drug interactions

• Other nephrotoxins (aminoglycosides, NSAIDs, cisplatin): markedly additive renal injury — avoid
• Corticosteroids / potassium-wasting diuretics: worsen hypokalaemia
• Digoxin: hypokalaemia potentiates digoxin toxicity
• Skeletal muscle relaxants: enhanced by hypokalaemia

Pregnancy and lactation

Used in human pregnancy for life-threatening mycoses (considered one of the safer systemic antifungals there); veterinary data limited — reserve for serious disease and monitor.

Monitoring

• Renal values (BUN/creatinine) before EVERY dose — withhold/adjust if azotaemia worsens
• Serum potassium and magnesium (supplement as needed)
• PCV/haematocrit (anaemia) on prolonged therapy
• Hydration and urine output; infusion-reaction signs (temperature)
• Cumulative dose tracking toward the therapeutic target

Toxicity and overdose

Nephrotoxicity is the defining, cumulative-dose-related toxicity — azotaemia, renal tubular acidosis, hypokalaemia/hypomagnesaemia, and potentially irreversible renal failure. Acute infusion reactions (fever, rigors, vomiting) and, with rapid administration, cardiac arrhythmia/arrest also occur. Anaemia develops with prolonged therapy.

Management: No specific antidote. Stop the drug; aggressive IV crystalloid (saline) diuresis to support the kidneys, correct potassium/magnesium, and provide intensive supportive care. Switch to a lipid formulation or an azole for ongoing therapy. Treat infusion reactions with pre-medication (antihistamine/antipyretic) and slower administration; manage arrhythmia conventionally.

Clinical pearls

• Think in CUMULATIVE dose, not single dose: small increments 2–3×/week to a target total, with renal values dictating each dose
• Saline-load before and after every dose — diuresis is the single best way to limit nephrotoxicity
• Lipid/liposomal amphotericin is far kinder to the kidneys (and allows higher dosing) — use it when affordable, especially in cats
• Reserve for severe/refractory systemic mycoses, then step down to an azole (e.g. itraconazole/fluconazole) for the long maintenance phase
• Never bolus and never mix conventional amphotericin in saline for reconstitution (precipitation) — follow the product's dextrose-based protocol

Mechanism of action

Binds ergosterol in the fungal cell membrane and forms transmembrane pores, causing leakage of potassium and other intracellular contents → fungal cell death (fungicidal). Its lower (but real) affinity for mammalian cholesterol, especially in renal tubular membranes, underlies the characteristic nephrotoxicity. Lipid formulations preferentially deliver the drug to fungal/reticuloendothelial sites and spare the kidney.

Formulations and products

• Conventional (deoxycholate) 50 mg vial (reconstitute)
• Liposomal (AmBisome) 50 mg vial
• Fungizone — 50 mg vial (conventional deoxycholate), IV (reconstitute) (human-label)
• AmBisome — 50 mg vial (liposomal), IV (reconstitute) (human-label)
• Amphotret — 50 mg vial, IV (reconstitute) (human-label)

Storage

Vials: refrigerate (2–8 °C), protect from light. Reconstitute per label; conventional amphotericin is incompatible with saline for reconstitution (use dextrose as directed) — follow the specific product instructions. Use promptly after reconstitution.

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 antifungals

• Caspofungin
• Clotrimazole
• Enilconazole
• Fluconazole
• Griseofulvin
• Itraconazole
• Ketoconazole
• Lime Sulfur (Lime Sulphur Dip)

Frequently asked questions