Fusidic Acid: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Fucidin, Fucithalmic, Sodium fusidate, Isathal

Species with doses

Dogs and Cats

Routes

Ocular

Last reviewed

1 October 2026

Indications

• Bacterial conjunctivitis / keratitis — staphylococcal (ophthalmic gel)
• Localised superficial staphylococcal pyoderma (topical)
• Bacterial otitis externa (Staph) — combination otic products
• Surface staphylococcal infections including some resistant strains

Fusidic Acid 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

• Bacterial conjunctivitis (ophthalmic gel): Label-sourced — neither Papich 5e nor Plumb’s has a fusidic acid monograph; follow the product label (continue about 48 h after clinical resolution). Mainly Gram-positive (staphylococcal) cover.

Cats

• Bacterial conjunctivitis: Label-sourced — no Papich 5e or Plumb’s monograph; follow the product label. Does not treat Chlamydia or herpesvirus.

Contraindications

Known hypersensitivity. Use as systemic monotherapy (resistance develops rapidly — and systemic fusidic acid is hepatotoxic, so it is generally avoided systemically in animals). Deep/systemic infection needing systemic therapy. Otic use with a perforated eardrum (check the combination product).

Adverse effects

• Local irritation / stinging
• Contact hypersensitivity (occasional)
• Resistance selection with prolonged/monotherapy use

Drug interactions

• No significant systemic drug interactions (topical use)
• Combination with a corticosteroid (skin/ear products) for inflammation
• Avoid combining with other agents that select resistance unnecessarily

Pregnancy and lactation

Topical use is low-risk (negligible systemic absorption).

Monitoring

• Ocular/skin clinical response (resolution of staphylococcal infection)
• Local tolerance
• Avoid prolonged solo courses (resistance) — re-evaluate if not improving

Toxicity and overdose

Topical use is very safe — local irritation only. (Systemic fusidic acid, used in human medicine, is hepatotoxic and prone to rapid resistance, which is why veterinary use is topical.) The main concern is resistance selection with prolonged or monotherapy use.

Management: Rinse/discontinue for local irritation; supportive. No specific antidote needed for topical use.

Clinical pearls

• A potent topical anti-staphylococcal — the viscous 1 % ophthalmic gel gives long contact time, allowing once/twice-daily dosing for bacterial conjunctivitis
• Active against many methicillin-resistant staphylococci on the surface — useful for resistant superficial pyoderma/otitis (often with a steroid)
• Keep it topical and short-course: systemic fusidic acid is hepatotoxic and resistance develops fast with monotherapy
• A unique mechanism means no cross-resistance — but steward it to keep that advantage

Mechanism of action

Inhibits bacterial protein synthesis by binding elongation factor G (EF-G), preventing its release from the ribosome after GTP hydrolysis and thereby blocking the translocation step — bacteriostatic (bactericidal at high local concentrations). It has a unique mechanism (no cross-resistance with other classes) and concentrates well in skin and ocular tissues, with particularly strong activity against staphylococci.

Formulations and products

• Ophthalmic gel 1 % (viscous, Fucithalmic/Isathal)
• Topical cream/ointment 2 %
• Otic / skin combination (with steroid)
• Fucithalmic Vet / Isathal (Dechra / Leo) — 1 % ophthalmic gel, Ophthalmic gel
• Fucidin — 2 % cream/ointment; 1 % eye drops, Topical / ophthalmic (human-label)

Storage

Ophthalmic gel / topical: 15–25 °C; discard ophthalmic gel ~4 weeks after opening. 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 antibiotics

• Doxycycline
• Enrofloxacin
• Erythromycin
• Florfenicol
• Gamithromycin
• Gentamicin
• Levofloxacin
• Lincomycin

Frequently asked questions