Gentamicin Sulfate

What is this medication for?

• Serious gram-negative aerobic infections / staphylococci when safer drugs lack susceptibility or empiric coverage is urgent (sepsis, soft tissue/orthopedic, bacteremia)
• Brucellosis combination protocol (with minocycline/doxycycline)

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Gentamicin assay artifact: beta-lactams falsely lower stored-sample levels — freeze samples, draw at beta-lactam trough.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Neuromuscular blockade (Myasthenia gravis risk)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Nephrotoxicity — worse than amikacin (Tubular tissue death; usually reversible if stopped early)
• Ototoxicity — leans VESTIBULAR (vs amikacin's auditory) (May be irreversible)

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Same risk set as amikacin: renal disease, neonate/geriatric, dehydration/fever/sepsis, working dogs, sighthounds (reduce dose); rabbits contraindicated

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Loop/osmotic diuretics (furosemide, torsemide, mannitol)
  • Other kidney damage (amphotericin B, cisplatin, polymyxin B, vancomycin)
  • Cephalosporins
  • Beta-lactams
  • Neuromuscular blockers/anesthetics

Storage and handling

Room temperature; never mix with beta-lactams in the same solution (inactivation); ophthalmic/injectable formulations.

Good to know

• Gentamicin = vestibular ototoxicity; amikacin = auditory — either can do both, but the exam leans this way. Cats: vestibular sensitivity.
• Once-daily dosing logic identical to amikacin (peaks drive kill; low troughs spare the kidney) — exceptions: low infection-fighting cell counts (every 8 hours), renal impairment (extend interval + TDM).
• Gentamicin assay artifact: beta-lactams falsely lower stored-sample levels — freeze samples, draw at beta-lactam trough.
• Brucellosis protocol: gentamicin 5 mg/kg under the skin once daily weeks 1 & 4 + minocycline (or doxycycline) 25 mg/kg by mouth once daily × 4 weeks, repeated courses with serologic monitoring.