Tobramycin: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Tobrex, Tobracin, Tobramycin sulphate

Species with doses

Dogs, Cats, Horses, Birds, Reptiles and Camelids

General dose range

9–14 mg/kg IV q24h — check the species tables for the indication

Routes

IV, Ocular, IM

Last reviewed

1 October 2026

Indications

• Bacterial keratitis / conjunctivitis — Gram-negative incl. Pseudomonas (ophthalmic)
• Pseudomonas lower-airway infection (nebulised)
• Serious resistant Gram-negative systemic infection (culture-confirmed, with monitoring)
• Gentamicin-resistant Gram-negative infections (some)

Tobramycin 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

• Susceptible Gram-negative infection (systemic): Papich 5e: 9–14 mg/kg q24h SC, IM or IV. Plumb’s p.1127: give the total daily dose once daily; persistent bacteraemia 9–15 mg/kg q24h for ≤7 days (Greene). Hydrate, check creatinine before and during therapy and limit courses; therapeutic drug monitoring recommended. Reserve for resistant Gram-negatives.
• Bacterial keratitis / ocular surface infection (ophthalmic): Plumb’s 10e p.1406 (Tobramycin Ophthalmic, extra-label): susceptible ocular surface infections — 1 drop or a ¼–½ inch strip in the affected eye(s) 4 to 6 times daily; frequency may be increased to every 30–60 minutes for significant infections (e.g. Pseudomonas melting ulcers), then tapered. With a tobramycin/glucocorticoid combination for inflamed conjunctiva or after ocular surgery: 3–4 times daily. Papich 5e doses only the systemic drug.

Cats

• Susceptible Gram-negative infection: Papich 5e: 5–8 mg/kg q24h SC, IM or IV. Plumb’s p.1127 (Greene): 4–6 mg/kg q24h for 5 days or less. Cats are aminoglycoside-sensitive — hydrate and monitor renal and vestibular function.

Horses

• Pseudomonas / resistant Gram-negative infection: Papich 5e: 4 mg/kg IV or IM once daily reaches targets for most bacteria; 7.2 mg/kg is needed for organisms at the 4 µg/mL breakpoint. Plumb’s p.1127 (Hubenov 2007): 4 mg/kg q24h. No nebulisation dose is given in either reference. Monitor renal function.

Birds

• Susceptible infection: Plumb’s p.1127: 5 mg/kg IM q12h (Bauck & Hoefer); 2.5–5 mg/kg/day parenterally (Flammer). Hydrate.

Reptiles

• Susceptible infection: Plumb’s p.1127 (Gauvin 1993): 2.5 mg/kg IM once daily. Keep hydrated and warm.

Camelids

• Susceptible infection: Plumb’s p.1127 (Baird 2003): llamas 4 mg/kg IV q24h (or 0.75 mg/kg IV q8h). Aminoglycoside residues persist — obtain a FARAD withdrawal.

Contraindications

Pre-existing renal impairment, dehydration, or vestibular/auditory disease (systemic use). Concurrent nephrotoxins/ototoxins or neuromuscular blockers. Myasthenia gravis. Rapid IV bolus (neuromuscular blockade). Known aminoglycoside hypersensitivity. Ophthalmic use with corneal perforation (unless indicated).

Species-specific warnings

Cats: Cats are prone to aminoglycoside vestibulotoxicity/nephrotoxicity — use lower doses, ensure hydration, and avoid prolonged courses.

Adverse effects

• Nephrotoxicity (proximal tubular) — cumulative, dose-related (systemic)
• Ototoxicity — vestibular/cochlear (often irreversible)
• Neuromuscular blockade (rapid IV / with anaesthetics)
• Ophthalmic: transient local irritation

Drug interactions

• Loop diuretics (furosemide): additive oto-/nephrotoxicity
• Other nephrotoxins (NSAIDs, amphotericin B, cephalosporins): cumulative renal injury
• Neuromuscular blockers/anaesthetics: potentiated, prolonged paralysis
• Beta-lactams (anti-Pseudomonal penicillins): synergy — but do NOT mix in one syringe (inactivation)

Pregnancy and lactation

Aminoglycosides cross the placenta and risk fetal oto-/nephrotoxicity — avoid systemic use in pregnancy unless life-threatening infection with no alternative.

Monitoring

• Renal function (creatinine, urine sediment) before and during systemic therapy
• Hydration; vestibular/auditory signs
• Trough levels where available (minimise accumulation); shortest effective course
• Culture confirming a susceptible resistant Gram-negative

Toxicity and overdose

Systemic: cumulative nephrotoxicity (rising creatinine, casts, isosthenuria) and irreversible ototoxicity (head tilt, ataxia, deafness), risk rising with duration >7–10 days, dehydration, trough accumulation and concurrent nephro-/ototoxins. Rapid IV can cause neuromuscular blockade/respiratory paralysis. Ophthalmic/nebulised use has low systemic toxicity.

Management: No true antidote. Stop the drug; aggressive IV fluid diuresis to support renal clearance. For neuromuscular blockade: IV calcium and ventilatory support (neostigmine unreliable). Haemodialysis can remove drug in severe renal failure. Monitor renal values and hearing/vestibular signs.

Clinical pearls

• Reach for tobramycin (over gentamicin) mainly for PSEUDOMONAS — ophthalmic Tobrex for Gram-negative/melting corneal ulcers, or nebulised for Pseudomonas pneumonia (high lung, low systemic levels)
• Systemic use is a reserve, culture-driven decision — dose ONCE daily, keep the patient hydrated, and monitor renal values
• Never mix with a beta-lactam in the same syringe (aminoglycoside inactivation), though the pair is synergistic given separately
• Cats and dehydrated patients are at higher toxicity risk — dose conservatively and limit duration

Mechanism of action

Binds irreversibly to the 30S bacterial ribosomal subunit, causing mRNA misreading and inhibition of protein synthesis — concentration-dependent bactericidal killing with a post-antibiotic effect. Uptake is oxygen-dependent (poor activity against anaerobes/in abscesses). Its structure gives slightly enhanced anti-Pseudomonas activity versus gentamicin. Nephro- and ototoxicity arise from drug accumulation in renal tubular and inner-ear cells.

Formulations and products

• Injection 40 mg/mL
• Ophthalmic solution 3 mg/mL (0.3 %)
• Nebuliser solution (Pseudomonas pneumonia)
• Tobrex — 0.3 % eye drops/ointment, Ophthalmic (human-label)
• Tobramycin injection — 40 mg/mL, Injection (human-label)

Storage

Injection/ophthalmic: 15–30 °C, protect from light. Reconstituted/nebuliser solution per label.

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

• Tiamulin
• Tildipirosin
• Tilmicosin
• Tinidazole
• Trimethoprim / Sulfadiazine (TMP-Sulfa)
• Tulathromycin
• Tylvalosin
• Vancomycin

Frequently asked questions