Gentamicin is an aminoglycoside antibacterial used for serious infections caused by susceptible organisms, particularly aerobic gram-negative bacilli. Parenteral treatment is used in selected companion-animal and equine patients, sometimes in combination with a beta-lactam. Local formulations have ophthalmic, otic or other site-specific uses, while oral livestock products target intestinal rather than systemic infections.
Gentamicin enters susceptible bacteria and binds the 30S ribosomal subunit, causing misreading of messenger RNA and disruption of protein synthesis. Interaction with the gram-negative outer membrane also impairs membrane integrity and facilitates uptake. These combined effects produce rapid, concentration-dependent bacterial killing with a post-antibiotic effect. Cellular uptake depends on conditions supporting energy-dependent transport, contributing to its activity against aerobic organisms.
Greyhound regimen; applicability to other sighthounds is less established.
Sighthound bacterial infection
9 mg/kg
SC, IM
Every 24 h
Greyhound regimen; applicability to other sighthounds is less established.
Cat
Use / stage
Dose
Route
Schedule
Instructions
Bacterial infection
5–8 mg/kg
SC, IM, IV
Every 24 h
Do not use in: Renal insufficiency
Horse
Use / stage
Dose
Route
Schedule
Instructions
Adult bacterial infection
4–6.6 mg/kg
IM, IV
Every 24 h
Do not use in: Renal insufficiency
Neonatal foal infection
12–14 mg/kg
IM, IV
Every 24 h
Do not use in: Renal insufficiency; Foals younger than 2 weeks.
Pig
Use / stage
Dose
Route
Schedule
Instructions
Young-pig bacterial infection
15 mg/kg
SC, IM
Every 24 h
Do not use in: Renal insufficiency
Older-pig bacterial infection
10 mg/kg
SC, IM
Every 24 h
Do not use in: Renal insufficiency
Enteric infection
Reference only
PO
Do not use in: Renal insufficiency; 1.1–2.2 mg/kg in drinking water for 3 days; source does not clearly define dose frequency or water-intake assumptions.
Medicated-water colibacillosis treatment
Reference only
PO
1.1 mg/kg/day in drinking water for three days; the source gives 25 mg per gallon. Consumption-dependent dosing must be reconciled with body weight and actual water intake.
Medicated-water dysentery treatment
Reference only
PO
2.2 mg/kg/day in drinking water for three days; the source gives 50 mg per gallon. Water-intake-based medication cannot be flattened into a bolus dose.
Cattle
Use / stage
Dose
Route
Schedule
Instructions
Neonatal calf infection
12–15 mg/kg
IV, IM
Every 24 h
Do not use in: Renal insufficiency; Calves younger than 2 weeks; prolonged residue concerns.
Adult bacterial infection
5–6 mg/kg
IM, IV
Every 24 h
Do not use in: Renal insufficiency
Chinchilla
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
2–4 mg/kg
SC, IM
Every 8–24 h
Maintain hydration; monitor for nephrotoxicity and ototoxicity.
Gerbil
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
2–4 mg/kg
SC, IM
Every 8–24 h
Maintain hydration; monitor for nephrotoxicity and ototoxicity.
Guinea Pig
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
2–4 mg/kg
SC, IM
Every 8–24 h
Maintain hydration; monitor for nephrotoxicity and ototoxicity.
Hamster
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
2–4 mg/kg
SC, IM
Every 8–24 h
Maintain hydration; monitor for nephrotoxicity and ototoxicity.
Mouse
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
2–4 mg/kg
SC, IM
Every 8–24 h
Maintain hydration; monitor for nephrotoxicity and ototoxicity.
Rat
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
2–4 mg/kg
SC, IM
Every 8–24 h
Maintain hydration; monitor for nephrotoxicity and ototoxicity.
Ferret
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
5 mg/kg
SC, IM
Every 24 h
Use only when susceptibility and clinical need justify the nephrotoxicity risk.
Rabbit
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
5–8 mg/kg
SC, IM, IV
Every 24 h
For IV use, the described regimen dilutes into 4 mL/kg saline and infuses over 20 minutes. Monitor renal function.
Ratite
Use / stage
Dose
Route
Schedule
Instructions
Susceptible bacterial infection
5 mg/kg
IM
Every 24 h
Last-resort option because visceral gout can occur.
Parenteral treatment of serious susceptible aerobic bacterial infections in dogs, cats and horses, including selected gram-negative sepsis, respiratory, urinary or soft-tissue infections.
Combination treatment of selected severe bacterial infections, including neonatal foal sepsis, when an aminoglycoside component is appropriate.
Local treatment of susceptible bacterial ocular, otic or other focal infections with a corresponding veterinary formulation.
Oral treatment or control of susceptible Escherichia coli-associated colibacillosis in pigs with an indicated product.
Treatment or control of susceptible swine dysentery with an oral gentamicin product carrying that indication.
Monitor renal parameters, urinalysis and drug concentrations where available. Once-daily trough should be very low; impaired clearance requires reassessment.
Food-animal systemic use can leave very prolonged renal residues; do not apply short oral-product withdrawal times to injections.
