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.
กลไกการออกฤทธิ์: 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 → interferes with the initiation complex between mRNA and the ribosome → causes misreading of the genetic code → produces nonfunctional proteins → 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.
ขนาดยาตามชนิดสัตว์
- Empiric therapy · 10-15 mg/kg · IV/IM/SC · Not specified · Route not specified, assume IV, IM or SC
- Susceptible infections · 15 mg/kg (route not specified) once daily (q24h). Neutropenic or immunocompromised patients may still need to be dosed q8h (dose divided). · Not specified · q24h (or q8h)
- Sepsis · 20 mg/kg once daily IV · IV · q24h
- Susceptible infections · 8-16 mg/kg IM or IV once daily · IM/IV · q24h
- Susceptible infections · 8-16 mg/kg/day SC, IM, IV divided q8-24h · SC/IM/IV · q8-24h
- Susceptible infections · 10 mg/kg IM q8h or 25 mg/kg q12h · IM · q8h or q12h
- Susceptible infections · 22 mg/kg/day IM divided three times daily · IM · TID
- Susceptible infections · 21 mg/kg IV or IM once daily (q24h) · IV/IM · q24h
- Susceptible infections (Neonatal foals) · 21 mg/kg IV once daily · IV · q24h
วิธีการให้ยา
ข้อห้ามใช้
- Hypersensitivity to aminoglycosides
- Generally contraindicated in rabbits/hares (adversely affects GI flora balance)
อาการไม่พึงประสงค์
- Nephrotoxicity (tubular necrosis)
- Ototoxicity (auditory and vestibular)
- Neuromuscular blockade
- Facial edema
- Injection site pain/inflammation
- Peripheral neuropathy
- Hypersensitivity reactions
อันตรกิริยาระหว่างยา
- Beta-lactam antibiotics (penicillins, cephalosporins) · 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 · 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) · Concurrent use may increase the nephrotoxic or ototoxic potential of the aminoglycosides.
- NSAIDs · May cause nephrotoxic effects; concurrent use with aminoglycosides should generally be avoided.
- Other Nephrotoxic Drugs (e.g., cisplatin, amphotericin B, polymyxin B, vancomycin) · Potential for increased risk for nephrotoxicity.
- Neuromuscular blocking agents & General anesthetics · Concomitant use could potentiate neuromuscular blockade.
การติดตาม
- 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
การได้รับยาเกินขนาด
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.
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