Amphotericin B
Also known as: Abelcet · AmBisome · Amphotec · Fungizone · Amphocil · Amphotericin B deoxycholate · Amphotericin B lipid complex · Liposomal amphotericin B · Anfotericina B · Amphotericinum B
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible systemic fungal infections (Rapid-Infusion Technique) | 0.25 mg/kg IV over 5 minutes, then 0.5 mg/kg 3 times a week until 9-12 mg/kg accumulated dosage is given | IV | 3 times a week | Until 9-12 mg/kg accumulated | 🌎 NA |
| Susceptible systemic fungal infections (Slow IV Infusion Technique) | 0.25 mg/kg IV over 4-6 hours, then 0.5 mg/kg 3 times a week until 9-12 mg/kg accumulated dosage is given | IV | 3 times a week | Until 9-12 mg/kg accumulated | 🌎 NA |
| Systemic fungal infections (Dehydrated/compromised) | 0.5 mg/kg diluted in D5W given by slow IV over 15 minutes (normal renal) or 3-6 hours (compromised renal) | IV | Every other day | Until cumulative dose of 8-10 mg/kg (or higher depending on disease) | 🌎 NA |
| Systemic mycoses (Lipid-based: AmBisome, Amphocil, Abelcet) | Test dose of 0.5 mg/kg; then 1-2.5 mg/kg IV q48h (or Monday, Wednesday, Friday) for 4 weeks or until the total cumulative dose is reached | IV | q48h | 4 weeks or until cumulative dose reached | 🌎 NA |
| Systemic mycoses (ABLC; Abelcet) | 2-3 mg/kg IV three days per week for a total of 9-12 treatments (cumulative dose of 24-27 mg) | IV | 3 days per week | 9-12 treatments | 🌎 NA |
| Blastomycosis | 0.5 mg/kg 3 times weekly until a total dose of 6 mg/kg is given | IV | 3 times weekly | Until 6 mg/kg cumulative | 🌎 NA |
| Blastomycosis | 0.15-0.5 mg/kg IV 3 times a week | IV | 3 times a week | Until total dose reaches 4-6 mg/kg, then start maintenance | 🌎 NA |
| Blastomycosis (severe cases, using Abelcet) | 1-2 mg/kg IV three times a week (or every other day) to a cumulative dose of 12-24 mg/kg | IV | 3 times a week | Until 12-24 mg/kg cumulative | 🌎 NA |
| Cryptococcosis | 0.5-0.8 mg/kg SC 2-3 times per week | SC | 2-3 times per week | — | 🌎 NA |
| Histoplasmosis | 0.15-0.5 mg/kg IV 3 times a week | IV | 3 times a week | Until total dose reaches 2-4 mg/kg, then start maintenance | 🌎 NA |
| Histoplasmosis | 0.5 mg/kg IV given over 6-8 hours. If dose is tolerated, increase to 1 mg/kg given on alternate days until total dose of 7.5-8.5 mg/kg cumulative dose is achieved | IV | Alternate days | Until 7.5-8.5 mg/kg cumulative | 🌎 NA |
| Leishmaniasis (Liposomal form) | 3-3.3 mg/kg IV 3 times weekly for 3-5 treatments | IV | 3 times weekly | 3-5 treatments | 🌎 NA |
| Leishmaniasis (AmBisome) | Give initial test dose of 0.5 mg/kg, then 3-3.3 mg/kg IV every 72-96 hours until a cumulative dose of 15 mg/kg is reached | IV | q72-96h | Until 15 mg/kg cumulative | 🌎 NA |
| Gastrointestinal pythiosis (ABLC; Abelcet) | 1-2 mg/kg IV three times weekly for 4 weeks (cumulative dose 12-24 mg) | IV | 3 times weekly | 4 weeks | 🌎 NA |
| Systemic fungal infections and leishmaniosis | Dose not specified in monograph; requires specific protocols | IV | As directed | Until clinical resolution | 🌍 EU |
- Susceptible systemic fungal infections (Rapid-Infusion Technique): Dilute in 30 mL of 5% dextrose. Flush with 10 mL D5W before and after.
- Susceptible systemic fungal infections (Slow IV Infusion Technique): Dilute in 250-500 mL of D5W.
- Systemic fungal infections (Dehydrated/compromised): Must rehydrate before administration. Discontinue if BUN exceeds 50 mg/dL.
- Systemic mycoses (Lipid-based: AmBisome, Amphocil, Abelcet): 1 mg/kg for susceptible yeast/dimorphic fungi (cumulative 12 mg/kg); 2-2.5 mg/kg for resistant filamentous fungi (cumulative 24-30 mg/kg).
- Systemic mycoses (ABLC; Abelcet): Dilute to 1 mg/mL in D5W and infuse over 1-2 hours.
- Blastomycosis: Given with ketoconazole.
- Blastomycosis: Given with ketoconazole.
- Cryptococcosis: Diluted in 0.45% NaCl with 2.5% dextrose. Concentrations >20 mg/L result in local irritation/sterile abscess.
- Histoplasmosis: Given with ketoconazole.
- Histoplasmosis: Alternative to ketoconazole treatment.
- Gastrointestinal pythiosis (ABLC; Abelcet): Follow-up medical therapy after surgical resection.
- Systemic fungal infections and leishmaniosis: Lipid formulations preferred if pre-existing renal insufficiency exists.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible systemic fungal infections (Rapid-Infusion Technique) | 0.25 mg/kg IV over 5 minutes 3 times a week until 9-12 mg/kg accumulated dosage is given | IV | 3 times a week | Until 9-12 mg/kg accumulated | 🌎 NA |
| Cryptococcosis | 0.25 mg/kg in 30 mL D5W IV over 15 minutes q48h | IV | q48h | 3-4 weeks after clinical signs resolve | 🌎 NA |
| Cryptococcosis | 0.15-0.4 mg/kg IV 3 times a week | IV | 3 times a week | Until total dose reaches 4-6 mg/kg, then start maintenance | 🌎 NA |
| Cryptococcosis | 0.5-0.8 mg/kg SC 2-3 times per week | SC | 2-3 times per week | — | 🌎 NA |
| Cryptococcosis (ABLC; Abelcet) | 1 mg/kg IV three days per week for a total of 12 treatments (cumulative dose of 12 mg) | IV | 3 days per week | 12 treatments | 🌎 NA |
| Histoplasmosis | 0.25 mg/kg in 30 mL D5W IV over 15 minutes q48h | IV | q48h | 4-8 weeks | 🌎 NA |
| Histoplasmosis | 0.15-0.5 mg/kg IV 3 times a week | IV | 3 times a week | Until total dose reaches 2-4 mg/kg, then start maintenance | 🌎 NA |
| Blastomycosis | 0.25 mg/kg in 30 mL D5W IV over 15 minutes q48h | IV | q48h | Until cumulative dose of 4 mg/kg is given | 🌎 NA |
| Blastomycosis | 0.15-0.5 mg/kg IV 3 times a week | IV | 3 times a week | Until total dose reaches 4-6 mg/kg, then start maintenance | 🌎 NA |
| Systemic fungal infections (e.g., cryptococcosis) | Dose not specified in monograph; requires specific protocols | IV | As directed | Until clinical resolution | 🌍 EU |
| Cryptococcosis (when IV access is problematic) | Dose not specified in monograph; requires specific protocols | SC | As directed | Until clinical resolution | 🌍 EU |
- Susceptible systemic fungal infections (Rapid-Infusion Technique): Dilute in 30 mL of 5% dextrose. Flush with 10 mL D5W before and after.
- Cryptococcosis: Given with flucytosine. Stop if BUN >50 mg/dL.
- Cryptococcosis: Given with flucytosine.
- Cryptococcosis: Diluted in 0.45% NaCl with 2.5% dextrose (400 mL for cats).
- Cryptococcosis (ABLC; Abelcet): Dilute to 1 mg/mL in D5W and infuse over 1-2 hours.
- Histoplasmosis: Given with ketoconazole. Stop if BUN >50 mg/dL.
- Histoplasmosis: Given with ketoconazole.
- Blastomycosis: Given with ketoconazole. Stop if BUN >50 mg/dL.
- Blastomycosis: Given with ketoconazole.
- Systemic fungal infections (e.g., cryptococcosis): SC alternative has been used for cryptococcosis if regular venous catheterization is problematic.
- Cryptococcosis (when IV access is problematic): SC route used as an alternative to IV.
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible systemic fungal infections (Rabbits) | 1 mg/kg/day IV | IV | q24h | — | 🌎 NA |
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Aspergillosis (raptors and psittacines) | 1.5 mg/kg IV three times daily for 3 days | IV | q8h | 3 days | 🌎 NA |
| Aspergillosis (raptors and psittacines) | 1 mg/kg diluted in sterile water once to 3 times daily for 3 days | Intratracheal | q8-24h | 3 days | 🌎 NA |
| Aspergillosis | 1.5 mg/kg IV q12h for 3-5 days; topically in the trachea at 1 mg/kg q12h; 0.3-1 mg/mL nebulized for 15 minutes 2-4 times daily | IV/Intratracheal/Nebulization | Variable | 3-5 days (IV) | 🌎 NA |
| Macrorhabdiasis (Microrhabdus ornithogaster) | 100-150 mg/kg PO q12h for 30 days | PO | q12h | 30 days | 🌎 NA |
- Aspergillosis (raptors and psittacines): With or followed by flucytosine.
- Aspergillosis (raptors and psittacines): In conjunction with flucytosine.
- Macrorhabdiasis (Microrhabdus ornithogaster): Treatment failures common with shorter durations.
Reptiles
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible fungal respiratory infections | 1 mg/kg diluted in saline and given intra-tracheally once daily for 14-28 treatments | Intratracheal | q24h | 14-28 treatments | 🌎 NA |
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Fungal pneumonia | Day 1: 0.3 mg/kg IV; Day 2: 0.4 mg/kg IV; Day 3: 0.6 mg/kg IV; days 4-7: no treatment; then every other day until a total cumulative dose of 6.75 mg/kg has been administered | IV | Variable | Until 6.75 mg/kg cumulative | 🌎 NA |
| Phycomycoses and pulmonary mycoses | Day 1: 0.3 mg/kg IV; Day 2: 0.45 mg/kg IV; Day 3: 0.6 mg/kg IV; then every other day for 3 days per week (MWF or TTHSa) | IV | Variable | 10-80 days | 🌎 NA |
| Intrauterine infusion | 200-250 mg | Intrauterine | q24h or q48h | 3-7 days | 🌎 NA |
- Phycomycoses and pulmonary mycoses: Administer in 1L D5W at 1 L/hr. Adjust if toxicity occurs.
- Intrauterine infusion: Little science available for recommending doses/diluents.
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible systemic fungal infections (Llama) | 1 mg test dose, then initially at 0.3 mg/kg IV over 4 hours... Subsequent doses were increased by 10 mg and given every 48 hours until reaching 1 mg/kg q48h IV for 6 weeks | IV | q48h | 6 weeks | 🌎 NA |
- Susceptible systemic fungal infections (Llama): Single case report in a Llama (Coccidioidomycosis).
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Amphotericin B is a potent, systemic polyene macrolide antifungal agent reserved for progressive, potentially fatal mycotic infections (e.g., blastomycosis, histoplasmosis, cryptococcosis, coccidioidomycosis).
Due to its poor oral bioavailability, it must be administered parenterally (typically IV). The conventional form, amphotericin B deoxycholate, is notorious for causing significant nephrotoxicity, which limits its use and requires intensive monitoring.
Newer lipid-based formulations (e.g., liposomal amphotericin B, amphotericin B lipid complex) encapsulate the drug in lipid vehicles. These formulations are significantly less nephrotoxic, allow for higher cumulative doses, and penetrate tissues (like lungs, liver, and spleen) better, though they are considerably more expensive.
Clinical Pearl: While highly effective against many dimorphic fungi, aspergillosis in dogs and cats often does not respond satisfactorily to amphotericin B therapy.
Mechanism of action
Amphotericin B is fungistatic or fungicidal depending on the concentration.
It works by binding to sterols—primarily ergosterol—in the fungal cell membrane. This binding creates transmembrane pores → alters membrane permeability → allows intracellular potassium (K+), magnesium, and other vital cellular constituents to leak out → leading to fungal cell death.
Toxicity Mechanism: Mammalian cell membranes contain cholesterol. While amphotericin B has a higher affinity for ergosterol, it still binds to mammalian cholesterol to some degree. This cross-reactivity, particularly in renal epithelial cells, is the primary mechanism behind its dose-limiting nephrotoxicity. It also induces renal vasoconstriction, leading to a decreased glomerular filtration rate (GFR).
Safety & warnings
Contraindications
- Patients with known hypersensitivity to amphotericin B (unless the infection is life-threatening and no alternatives exist)
Adverse effects
- Nephrotoxicity (very common, dose-dependent)
- Anorexia and vomiting
- Hypokalemia and hypomagnesemia
- Distal renal tubular acidosis
- Phlebitis at injection site
- Cardiac arrhythmias
- Non-regenerative anemia
- Fever (can be mitigated with NSAIDs or low-dose steroids)
- Tachycardia, tachypnea, lethargy, restlessness (horses)
- Calcinosis cutis (dogs)
Precautions
Black Box Warning Equivalent: Amphotericin B is highly nephrotoxic. Renal function must be aggressively monitored during therapy.
- Use with extreme caution in patients with pre-existing renal disease.
- Cats are more sensitive to nephrotoxic effects; reduced dosages are often recommended.
- Ensure adequate hydration prior to administration. Sodium loading (e.g., normal saline administration before and after dosing) may help avert renal insufficiency by preventing tubuloglomerular feedback-induced vasoconstriction.
- Pregnancy: Weigh risks vs. benefits. FDA Category B (human); Papich Class A (veterinary).
Drug interactions
May exacerbate the potassium-losing effects of amphotericin B.
Amphotericin B-induced hypokalemia may exacerbate digoxin toxicity.
In vitro synergy against Cryptococcus and Candida, but may also increase flucytosine toxicity.
Additive renal toxicity; avoid concurrent or sequential use if possible.
Increased risk of severe hypokalemia.
Reconstituting amphotericin B deoxycholate with these solutions may cause precipitation.
Amphotericin B-induced hypokalemia may enhance curariform effects.
Amphotericin may increase the toxic effects of fluorouracil.
Amphotericin may increase the toxic effects of doxorubicin.
Amphotericin may increase the toxic effects of methotrexate.
Concurrent use significantly increases the risk of severe nephrotoxicity.
Monitoring
- BUN and serum creatinine (before each dose or every other day during dose escalation, then at least weekly)
- Serum electrolytes including sodium, potassium, and magnesium (weekly)
- Liver function tests (weekly)
- CBC and Packed Cell Volume (PCV) (weekly)
- Urinalysis (weekly)
- Total plasma protein (TPP) (at least weekly)
- Body weight
Pharmacokinetics
Half-life
Absorption
Poorly absorbed from the GI tract; must be given parenterally (IV) for systemic infections.
Distribution
Penetrates well into most tissues but poorly into pancreas, muscle, bone, aqueous humor, and pleural/pericardial/synovial/peritoneal fluids unless inflamed. CSF levels are ~3% of serum levels. Highly protein bound (90-95%). Lipid forms have higher penetration into lungs, liver, and spleen.
Metabolism
Metabolic pathways are not fully known.
Elimination
Exhibits biphasic elimination. Approximately 2-5% of the drug is recovered in the urine in unchanged (biologically active) form. Can be detected in urine up to 7 weeks after therapy stops.
Overdose
Acute intravenous overdose reports are rare. Because of the severe toxicity of the drug, dosage calculations and solution preparation procedures must be double-checked.
If an accidental overdose occurs, renal toxicity is the primary concern. Toxicity may be minimized by aggressively administering intravenous fluids and mannitol to maintain GFR and promote diuresis.
Available products
Formulations
- Powder for injection (Deoxycholate)
- Suspension for injection (Lipid complex)
- Powder for injection (Liposomal/Cholesteryl sulfate complex)
- Topical formulations
Human-labeled
- Amphotericin B Desoxycholate Powder for Injection: 50 mg in vials
- Amphotericin B Lipid-Based Suspension for Injection: 100 mg/20 mL (Abelcet)
- Amphotericin B Lipid-Based Powder for Injection: 50 mg, 100 mg (Amphotec, AmBisome)
- Topical formulations (Fungizone)
Regulatory status
Human authorized products used under the cascade.
Human authorized products used under the cascade.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store un-reconstituted vials in the refrigerator (2-8°C), protected from light and moisture. Reconstitute with sterile water for injection (no preservatives). After reconstitution, stable for 24 hours at room temperature and 1 week refrigerated if protected from light. When diluted in D5W (pH >4.3) for IV use, protect from light during administration (though studies show potency remains largely unaffected for 8-24 hours of light exposure).
Client information
Amphotericin B is a powerful antifungal medication used only for serious, life-threatening fungal infections.
- Administration: It must be given by injection (usually IV), which often requires your pet to be hospitalized or make frequent visits to the clinic.
- Kidney Risks: This drug is highly toxic to the kidneys. Most pets will experience some degree of kidney stress. We will perform frequent blood and urine tests to monitor kidney function closely.
- Side Effects: Watch for signs of illness such as vomiting, loss of appetite, extreme lethargy, or fever. Contact your veterinarian immediately if these occur.
- Cost & Commitment: Treatment can be expensive and requires a significant time commitment for monitoring and administration.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.