Posaconazole: veterinary dose and monograph

At a glance

Drug class

Antifungal

Also known as

Noxafil, Posatrol, Posaconazole

Species with doses

Dogs and Cats

General dose range

5 mg/kg PO q24h (with food) — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Refractory / resistant invasive aspergillosis
• Mucormycosis (zygomycosis) — a key niche (other azoles inactive)
• Refractory or resistant candidiasis and other invasive mould infections
• CNS/ocular or disseminated mycoses unresponsive to first-line azoles

Posaconazole 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

• Invasive mycosis — oral suspension: Papich 5e: oral suspension 10 mg/kg PO q24h, with a fatty meal. Long courses; monitor liver enzymes; therapeutic drug monitoring (trough >0.5 µg/mL) helps. Plumb’s 10e p.1044 (extra-label): suspension 5–10 mg/kg PO every 12–24 hours (a preclinical study suggests 10 mg/kg/day is effective), given with food, preferably right after a high-fat meal. Suspension and delayed-release tablets are NOT interchangeable mg for mg.
• Invasive mycosis — delayed-release tablet: Papich 5e: delayed-release tablet 5 mg/kg PO initially q48h; some animals are extended to q72h or longer if troughs stay above 0.5 µg/mL. Plumb’s 10e p.1044 (extra-label, pharmacokinetic study): 5 mg/kg PO every 48 hours may be considered.

Cats

• Mild fungal infection / prevention: Papich 5e: oral suspension 15 mg/kg PO once, then 8 mg/kg PO q48h. Monitor liver enzymes and appetite.
• Severe invasive fungal infection: Papich 5e: oral suspension 30 mg/kg PO loading dose, then 15 mg/kg every other day. Plumb’s 10e p.1044 (extra-label) gives the same regimen. Long courses; monitor liver enzymes.
• Susceptible fungal infection — daily (after 15 mg/kg load): Plumb’s 10e p.1044 (extra-label): 15 mg/kg PO loading dose followed by 7.5 mg/kg PO every 24 hours. Give with food.
• Susceptible fungal infection — maintenance range: Plumb’s 10e p.1044 (extra-label): 5–7.5 mg/kg PO every 24 hours or divided into 2 doses per day. Give with food.

Birds

• No reference dose for this species: Neither Papich 5e nor Plumb’s 10e (pp.1043–1045 dose dogs and cats only) gives a posaconazole dose for birds.

Contraindications

Significant hepatic impairment. Concurrent drugs with dangerous CYP3A interactions / QT-prolonging agents (it strongly inhibits CYP3A and prolongs QT). Pregnancy (azole teratogenicity). Known azole hypersensitivity.

Species-specific warnings

Birds: Birds need higher mg/kg (species kinetic differences) — used for resistant aspergillosis; monitor liver and response.

Adverse effects

• Hepatotoxicity (raised liver enzymes)
• GI upset (vomiting, anorexia)
• QT prolongation
• Variable absorption (food/formulation-dependent)

Drug interactions

• Potent CYP3A4 inhibitor: raises levels of cyclosporine, tacrolimus, vincristine, benzodiazepines, etc.
• QT-prolonging drugs (cisapride, some antiarrhythmics): contraindicated combinations (torsades risk)
• CYP inducers (phenobarbital, rifampin): markedly lower posaconazole levels
• Acid-suppressants/food: affect suspension absorption

Pregnancy and lactation

Contraindicated/avoid in pregnancy — azole teratogenicity.

Monitoring

• Liver enzymes (baseline and periodically)
• ECG (QT) and electrolytes if cardiac risk / interacting drugs
• Therapeutic drug levels where available (erratic absorption)
• Clinical/antigen response; review co-medications for CYP/QT interactions

Toxicity and overdose

Hepatotoxicity and QT prolongation are the key toxicities; GI upset is common. Absorption (of the suspension) is erratic and food-dependent, so under-dosing/treatment failure is a practical risk — therapeutic drug monitoring helps. As with all azoles, the interaction burden is significant.

Management: No specific antidote. Discontinue; supportive care and hepatoprotection (SAMe/silybin) for hepatotoxicity; ECG and electrolyte management for QT effects. Decontaminate large recent ingestions. Effects resolve slowly given long half-life.

Clinical pearls

• The broadest azole — reach for it in refractory/itraconazole-resistant aspergillosis and especially MUCORMYCOSIS (where other azoles fail)
• Give the suspension WITH a fatty meal for absorption (or use the delayed-release tablet/IV); consider therapeutic drug monitoring — failures are often under-dosing
• A heavyweight CYP3A inhibitor that prolongs QT — scrutinise all co-medications (cyclosporine, vincristine, cisapride) before use
• Expensive and reserved — monitor the liver on long courses

Mechanism of action

Inhibits fungal cytochrome-P450 14-α-demethylase (CYP51), blocking ergosterol synthesis and damaging the fungal cell membrane. Its extended side-chain structure binds the enzyme more avidly and across a broader range of fungi than older azoles — crucially retaining activity against the Mucorales and itraconazole-resistant Aspergillus. It is a potent inhibitor of mammalian CYP3A4 (extensive interactions) and prolongs the QT interval.

Formulations and products

• Delayed-release tablet 100 mg
• Oral suspension 40 mg/mL
• IV infusion 18 mg/mL
• Noxafil — 100 mg DR tablet; 40 mg/mL suspension; 18 mg/mL IV, Tablet / suspension / IV (human-label)
• Posatrol — 40 mg/mL suspension; 100 mg tablet, Suspension / tablet (human-label)

Storage

Tablets: 15–30 °C, dry. Suspension: 15–30 °C, shake well, discard per label after opening. IV per label. Protect from light.

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

• Ketoconazole
• Lime Sulfur (Lime Sulphur Dip)
• Miconazole
• Nystatin
• Terbinafine
• Voriconazole

Frequently asked questions