Gentamicin: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Gentocin, Garamycin

Species with doses

Dogs, Cats, Horses, Pigs, Birds, Rabbits, Ferrets, Reptiles and Primates

General dose range

4–9 mg/kg IV q24h — check the species tables for the indication

Routes

IV, SC, PO, IM

Last reviewed

1 October 2026

Indications

• Serious gram-negative sepsis / bacteraemia
• Pyelonephritis / complicated UTI (susceptibility-guided)
• Equine bacterial endometritis (intrauterine infusion)
• Equine pleuropneumonia / R. equi (with beta-lactam)
• Bovine coliform mastitis (extra-label, country-dependent)
• Topical / ophthalmic gram-negative infections

Gentamicin 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

• Empirical gram-negative sepsis: Plumb’s p.569 (Greene 2006): bacteraemia/sepsis 6.6 mg/kg IV, IM or SC once daily for <7 days; orthopaedic/soft tissue 4.4–6.6 mg/kg. Hydrate before each dose; monitor urine sediment (casts) and creatinine/SDMA every 48 h.
• Empirical (extended once-daily): Papich 5e: 9–14 mg/kg q24h SC, IM or IV. Plumb’s p.569 (Autran de Morais 2009): empiric therapy 10–14 mg/kg once daily. Once-daily dosing maximises peak/MIC and reduces nephrotoxicity; therapeutic drug monitoring recommended; neutropenic patients may need q8h dosing.
• Localised UTI: Plumb’s p.569 (Greene 2006): localised urinary infections — first dose 4.4 mg/kg IM or SC, then 2.2 mg/kg once daily for 7–10 days.
• Sighthound — reduced dose: Plumb’s p.569 (KuKanich 2008): Greyhounds and probably other sighthounds 6 mg/kg IV q24h or 9 mg/kg SC/IM q24h (smaller volume of distribution).

Cats

• Empirical gram-negative: Papich 5e: 5–8 mg/kg q24h SC, IM or IV. Plumb’s p.569: 5–8 mg/kg once daily (Autran de Morais); 6–8 mg/kg once daily (Trepanier); 8 mg/kg once daily or 2–4 mg/kg q8h (Aucoin). Cats are sensitive to vestibular/ototoxicity and nephrotoxicity — keep courses short and hydrated.
• Bacteraemia / sepsis: Plumb’s p.569 (Greene 2006): bacteraemia/sepsis 4.4 mg/kg IV, IM or SC once daily for <7 days; urinary infections 2.2 mg/kg once daily.

Cattle

• NOT FDA-approved — extra-label discouraged: Use prohibited / strongly discouraged in food animals (USA): tissue residues persist >18 months. Withdrawal essentially indeterminate. Consult AMDUCA / FARAD before any use. For transparency: Papich 5e does list cattle doses (calves under 2 weeks 12–15 mg/kg q24h IV/IM; adult cattle 5–6 mg/kg q24h IM/IV), but U.S. veterinary bodies advise against aminoglycosides in cattle because of prolonged renal residues.

Horses

• Adult — susceptible infection: Papich 5e: adults 4–6.6 mg/kg q24h IM or IV. Plumb’s p.569 (Foreman; Chaffin; Haggett & Wilson): 6.6 mg/kg IV or IM once daily — IV preferred (IM can irritate muscle); intrauterine 1–2 g buffered (LeBlanc).
• Foal — susceptible infection: Plumb’s p.569 (Corley & Hollis 2009): foals 11–15 mg/kg q24h. Papich 5e: foals <2 weeks 12–14 mg/kg q24h IM or IV. Therapeutic drug monitoring strongly recommended.
• Pleuropneumonia (adult): Plumb’s p.569 (Sprayberry 2009): initially 8 mg/kg IV, adjusted by therapeutic drug monitoring, or 6.6 mg/kg IV or IM q24h.

Pigs

• Neonatal colibacillosis (label): Garacin Pig Pump: 5 mg PO once per piglet (label dose, not per-kg). FARAD recommends ≥40 day slaughter withdrawal for any extra-label parenteral use.
• Colibacillosis / swine dysentery — drinking water (label): Plumb’s p.570 (Garacin label) and Papich 5e: colibacillosis 1.1 mg/kg/day (25 mg/gallon) and swine dysentery 2.2 mg/kg/day (50 mg/gallon) in drinking water for 3 days. Papich also lists 15 mg/kg (young pigs) or 10 mg/kg (older pigs) SC/IM once daily.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• NOT FDA-approved — extra-label discouraged: Use prohibited / strongly discouraged in food animals (USA): tissue residues persist >18 months. Withdrawal essentially indeterminate. Consult AMDUCA / FARAD before any use. For transparency: Papich 5e does list cattle doses (calves under 2 weeks 12–15 mg/kg q24h IV/IM; adult cattle 5–6 mg/kg q24h IM/IV), but U.S. veterinary bodies advise against aminoglycosides in cattle because of prolonged renal residues.

Birds

• Susceptible Gram-negative (companion birds): Plumb's p.570: 2.5–5 mg/kg once daily (amikacin preferred to reduce toxicity). Ratites 5 mg/kg IM q24h — last resort only, causes visceral gout. Ensure hydration.

Rabbits

• Rabbit susceptible Gram-negative (USE CAUTIOUSLY): Plumb’s p.570 (Ivey & Morrisey 2000): rabbits 5–8 mg/kg total daily dose SC, IM or IV (may be divided q8–24h; once daily is more effective and less toxic). If IV, dilute in 4 mL/kg saline over 20 min. Nephrotoxic — hydrate and keep courses short. (2–4 mg/kg is Plumb’s RODENT dose.)

Ferrets

• Susceptible Gram-negative: Plumb's p.569 (Williams 2000): 4–8 mg/kg IM/SC/IV divided 2–3×/day; (Morrisey & Carpenter 2004): 5 mg/kg SC q24h. Use ONLY when culture demands — high nephrotoxicity risk.

Reptiles

• Snakes — bacterial gastritis: Plumb’s p.570 (Burke 1986): snakes 2.5 mg/kg IM every 72 hours (with oral neomycin 15 mg/kg and lactobacillus). Hydrate; monitor uric acid.
• Turtles — bacterial shell disease: Plumb’s p.570 (Rosskopf 1986): 5–10 mg/kg daily in water turtles, every other day in land turtles and tortoises, for 7–10 days, usually with a beta-lactam. Start with 20 mL/kg fluids; maintain hydration and monitor uric acid.

Primates

• Susceptible Gram-negative (monkeys): Carpenter Exotic Animal Formulary 6th ed, Table 13-1 (p.682): monkeys/chimpanzees 2–4 mg/kg IM/IV q12h; monkeys 3–5 mg/kg SC/IM q24h. Nephrotoxic/ototoxic — hydrate, short courses.

Contraindications

Pre-existing renal disease (relative — monitor closely with TDM and serum creatinine). NEVER use in food-producing animals in the United States — extremely prolonged tissue residues (>18 months); FDA strongly discourages extra-label use. CONTRAINDICATED or use only with extreme caution in rabbits, guinea pigs, chinchillas, hamsters — disrupts GI flora, fatal enterotoxaemia possible. Avoid in dogs/cats with botulism (potentiates neuromuscular blockade). Sighthound breeds need reduced dose (smaller volume of distribution). Cats are particularly sensitive to vestibular ototoxicity. Avoid concurrent loop diuretics (furosemide), amphotericin B, cisplatin — additive nephrotoxicity. Caution in working dogs (irreversible ototoxicity). IM injections in horses cause muscle irritation — IV preferred.

Species-specific warnings

Dogs: Severe Gram-negative infection only. Once-daily IV at 6–8 mg/kg. Mandatory hydration, daily renal monitoring. Maximum 7 days when possible.

Cats: More sensitive to nephro/ototoxicity than dogs. Once-daily 5–8 mg/kg. SC route causes tissue necrosis — IM or IV only. AVOID topical ophthalmic (corneal sequestrum).

Horses: Foal sepsis: 6.6 mg/kg IV q24h with beta-lactam. Adult horses: extra-label only — strict residue rules. NEVER in racehorses near competition (positive drug tests).

Cattle: PROHIBITED in lactating dairy in most jurisdictions. Meat withdrawal 18 MONTHS (US) — essentially eliminates food-animal use. Extra-label use is extra-cautious territory.

Birds: Caged birds tolerate 5–10 mg/kg IM q24h. Hydration critical. Topical use preferred for Pseudomonas keratitis in raptors.

Adverse effects

• Nephrotoxicity (proximal tubular necrosis) — usually reversible if caught early; monitor urine sediment, USG, BUN, creatinine
• Ototoxicity — vestibular signs in cats and dogs (often irreversible)
• Neuromuscular blockade — risk in myasthenia gravis, anaesthesia
• Pain / inflammation at IM injection site
• Hypersensitivity reactions (rare)

Drug interactions

• Loop diuretics (furosemide), other nephrotoxins (cisplatin, amphotericin B, NSAIDs, ACE-I): ADDITIVE NEPHROTOXICITY — avoid combination, monitor carefully
• Cephalosporins (especially cephalosporins at high doses): additive nephrotoxicity
• Penicillins / beta-lactams: synergistic against Enterococcus, Listeria — therapeutic combination but do NOT mix in same syringe (physical inactivation)
• Neuromuscular blockers (atracurium, succinylcholine): aminoglycosides enhance neuromuscular blockade — prolonged paralysis
• General anaesthesia: respiratory paralysis risk in patients receiving both
• Vancomycin: additive ototoxicity / nephrotoxicity
• Magnesium / calcium: high doses antagonise aminoglycoside neuromuscular effects

Pregnancy and lactation

AVOID — VESTIBULOTOXICITY and NEPHROTOXICITY in fetus. Crosses placenta. Use only when no alternative exists and benefit outweighs risk. FDA Category D (human). Streptomycin produced 8th cranial nerve damage in human infants — extrapolate caution.

Monitoring

• BUN, creatinine, urinalysis (proteinuria, glucosuria, granular casts) BEFORE every dose, then every 24–48 h during therapy
• Hydration status — NEVER dose a dehydrated patient
• Serum levels if possible: trough <2 µg/mL (once-daily dosing) confirms safety; peak 16–24 µg/mL = efficacy
• Vestibular signs (head tilt, ataxia, nystagmus), hearing changes — discontinue at first sign
• Withdrawal: cattle 18 mo meat, NEVER in dairy at any stage (USDA recommendation due to chronic residue concerns)
• Course duration: minimise to ≤7 days when possible

Toxicity and overdose

NEPHROTOXICITY: proximal tubular damage, acute kidney injury — risk increases with: dehydration, hypovolaemia, age, concurrent nephrotoxin, hypokalaemia, hypomagnesaemia, total dose, duration. Cats: more sensitive than dogs. OTOTOXICITY: vestibular (ataxia, head tilt, nystagmus) and cochlear (hearing loss) — often IRREVERSIBLE. Neuromuscular blockade in patients with myasthenia gravis or under general anaesthesia.

Management: No specific antidote. Discontinue immediately. Aggressive IV fluid diuresis to flush toxin from kidneys. Calcium gluconate for neuromuscular blockade reversal. Hemodialysis or peritoneal dialysis in severe AKI. Renal recovery may take weeks; ototoxicity usually permanent. Avoid further nephrotoxic exposure for 30 days.

Clinical pearls

• ONCE-DAILY DOSING (6–8 mg/kg IV/IM/SC q24h in dogs, 5–8 mg/kg in cats) is SAFER and MORE EFFECTIVE than divided dosing — exploits concentration-dependent killing + post-antibiotic effect, allows tubular drug-free interval for recovery
• Reserve for SEVERE Gram-negative infections (sepsis, pyelonephritis, life-threatening Pseudomonas)
• Combine with beta-lactam for synergy against Enterococcus / Listeria
• Topical use (otic / ophthalmic / wound) acceptable for resistant Pseudomonas — much less systemic risk
• NEVER in dehydrated patients — pre-treat with IV fluids if hypovolaemic
• Hydration before every dose — re-check renal parameters daily
• NEVER use SUBCUTANEOUSLY in cats — tissue necrosis. IV or IM only
• Cattle: very long meat withdrawal (18 months in US for systemic use) — essentially OFF the cattle formulary in US food chain
• Topical ophthalmic: AVOID in cats — corneal sequestrum risk reported

Mechanism of action

Aminoglycoside antibiotic. Binds the 30S bacterial ribosomal subunit, causing misreading of mRNA and inhibition of protein synthesis. Bactericidal, concentration-dependent killing with significant post-antibiotic effect — once-daily dosing exploits these pharmacokinetic properties and reduces toxicity vs. divided dosing. Excellent Gram-negative coverage (Pseudomonas, Klebsiella, E. coli, Enterobacter). Synergistic with beta-lactams against Enterococcus, Listeria. Poor anaerobic and Streptococcal coverage.

Formulations and products

• Gentocin injection 50 mg/mL
• Gentocin injection 100 mg/mL
• Ophthalmic solution 3 mg/mL
• Tylo-G Sure (Assure Biotech, Jagadhri (HR)) — Gentamicin 40 mg + Tylosin 200 mg per mL, Fixed combination injection

Storage

Injection: 15–25 °C, protect from light. Multidose vial: discard 28 days after broaching. Ophthalmic/otic: 15–25 °C. Reconstituted solutions 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

• Erythromycin
• Florfenicol
• Fusidic Acid
• Gamithromycin
• Levofloxacin
• Lincomycin
• Linezolid
• Marbofloxacin

Frequently asked questions