Amikacin Sulfate
Amikacin is a potent, semi-synthetic **aminoglycoside antibiotic** derived from kanamycin. It is primarily reserved for severe, multi-drug resistant (MDR) **gram-negative aerobic infections** (e.g., *Pseudomonas aeruginosa*, *E. coli*, *Klebsiella*, *Proteus*). Because it resists many of the enzymes that inactivate gentamicin, it is often effective against gentamicin-resistant strains. **Clinical Pearl:** Aminoglycosides exhibit concentration-dependent bactericidal activity and a significant post-antibiotic effect (PAE). Consequently, modern veterinary protocols strongly favor **once-daily (high-dose, extended-interval) dosing** to maximize peak concentrations (enhancing bacterial kill) while allowing trough levels to drop, which minimizes the risk of nephrotoxicity. It is inactive against fungi, viruses, and most anaerobic bacteria.
Mechanism: Amikacin actively transports across the bacterial cell membrane via an **oxygen-dependent mechanism** (which is why it is ineffective against anaerobic bacteria). Once inside, it binds irreversibly to the **30S ribosomal subunit**. Binding to 30S subunit โ interferes with the initiation complex between mRNA and the ribosome โ causes misreading of the genetic code โ produces nonfunctional proteins โ leads to rapid bacterial cell death. **Clinical Pearl:** Its antimicrobial activity is significantly enhanced in an alkaline environment and markedly reduced in purulent, acidic, or necrotic debris.
Dosing by species
- Empiric therapy ยท 10-15 mg/kg ยท IV/IM/SC ยท Not specified ยท Route not specified, assume IV, IM or SC
- Susceptible infections ยท 15 mg/kg (route not specified) once daily (q24h). Neutropenic or immunocompromised patients may still need to be dosed q8h (dose divided). ยท Not specified ยท q24h (or q8h)
- Sepsis ยท 20 mg/kg once daily IV ยท IV ยท q24h
- Susceptible infections ยท 8-16 mg/kg IM or IV once daily ยท IM/IV ยท q24h
- Susceptible infections ยท 8-16 mg/kg/day SC, IM, IV divided q8-24h ยท SC/IM/IV ยท q8-24h
- Susceptible infections ยท 10 mg/kg IM q8h or 25 mg/kg q12h ยท IM ยท q8h or q12h
- Susceptible infections ยท 22 mg/kg/day IM divided three times daily ยท IM ยท TID
- Susceptible infections ยท 21 mg/kg IV or IM once daily (q24h) ยท IV/IM ยท q24h
- Susceptible infections (Neonatal foals) ยท 21 mg/kg IV once daily ยท IV ยท q24h
Routes of administration
Contraindications
- Hypersensitivity to aminoglycosides
- Generally contraindicated in rabbits/hares (adversely affects GI flora balance)
Adverse effects
- Nephrotoxicity (tubular necrosis)
- Ototoxicity (auditory and vestibular)
- Neuromuscular blockade
- Facial edema
- Injection site pain/inflammation
- Peripheral neuropathy
- Hypersensitivity reactions
Drug interactions
- Beta-lactam antibiotics (penicillins, cephalosporins) ยท May have synergistic effects against some bacteria; potential for physical inactivation of aminoglycosides in vitro (do not mix together) and in vivo (patients in renal failure).
- Cephalosporins ยท Potentially could cause additive nephrotoxicity (controversial, well documented only with older agents like cephaloridine and cephalothin).
- Loop or Osmotic Diuretics (e.g., furosemide, torsemide, mannitol) ยท Concurrent use may increase the nephrotoxic or ototoxic potential of the aminoglycosides.
- NSAIDs ยท May cause nephrotoxic effects; concurrent use with aminoglycosides should generally be avoided.
- Other Nephrotoxic Drugs (e.g., cisplatin, amphotericin B, polymyxin B, vancomycin) ยท Potential for increased risk for nephrotoxicity.
- Neuromuscular blocking agents & General anesthetics ยท Concomitant use could potentiate neuromuscular blockade.
Monitoring
- Efficacy (cultures, clinical signs, WBCs)
- Therapeutic drug monitoring (TDM) is highly recommended: Peak level should be at least 40 mcg/mL and the 4-hour trough sample less than 10 mcg/mL
- Renal function tests (BUN, creatinine) and urinalysis (USG, casts) pre-therapy and repeated during therapy
- Gross monitoring of vestibular or auditory toxicity
Overdose
Should an inadvertent overdosage be administered, three treatments have been recommended: - **Hemodialysis:** Very effective in reducing serum levels but rarely a viable option for veterinary patients. - **Peritoneal dialysis:** Will reduce serum levels but is much less efficacious. - **Complexation:** Complexation of drug with either carbenicillin or ticarcillin (12-20 g/day in humans) is reportedly nearly as effective as hemodialysis.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.