Cefotaxime
Cefotaxime is a **third-generation parenteral cephalosporin** antibiotic with a broad spectrum of activity against both gram-positive and gram-negative bacteria. Key clinical features include: * **Extended Gram-Negative Coverage**: Highly effective against *Enterobacteriaceae* (e.g., *Klebsiella*, *E. coli*, *Salmonella*, *Proteus*). * **Anaerobic Activity**: Effective against many anaerobes including *Bacteroides fragilis* and *Clostridium* spp. * **CNS Penetration**: Unlike first- and most second-generation cephalosporins, cefotaxime achieves therapeutic concentrations in the **cerebrospinal fluid (CSF)** when the meninges are inflamed, making it a valuable option for bacterial meningitis and spinal cord infections. * **Administration**: Must be given parenterally (IV, IM, SC) as it is not appreciably absorbed orally. IV administration should be slow (over 3-5 minutes) to minimize adverse reactions. > **Clinical Pearl**: While it has excellent activity against many gram-negative aerobes, its efficacy against *Pseudomonas aeruginosa* is variable and often clinically disappointing. A 30-microgram cefotaxime disk should be used for Kirby-Bauer susceptibility testing.
Mecanismo: Cefotaxime is a **time-dependent, bactericidal** antibiotic. * **Mechanism**: It binds to specific **penicillin-binding proteins (PBPs)** located inside the bacterial cell wall → inhibits the third and final stage of bacterial cell wall peptidoglycan synthesis → leads to cell lysis and death mediated by bacterial cell wall autolytic enzymes (autolysins). * **Metabolism**: It is partially metabolized in the liver to **desacetylcefotaxime**, an active metabolite that works synergistically with the parent compound to enhance antibacterial activity.
Dosificación por especie
- Soft tissue infections · 22 mg/kg IV, IM or SC q8h for 7 days or less or 50 mg/kg IV or IM q12h for 7 days or less · IV, IM, SC · q8h or q12h · 7 days or less
- Orthopedic infections · 20-40 mg/kg IV, IM or SC q6-8h for 7 days or less · IV, IM, SC · q6-8h · 7 days or less
- Severe bacteremia · 20-80 mg/kg IV q6h or 10-50 mg/kg IV q4-6h for as long as necessary · IV · q4-6h · As long as necessary
- Susceptible infections · 25-50 mg/kg IV, IM or SC q8h · IV, IM, SC · q8h
- Sepsis · 20-80 mg/kg IV, IM q8h · IV, IM · q8h
- CNS infections (spinal cord) · 25 mg-50 mg/kg IV, IM q8h · IV, IM · q8h
- Acute sepsis or serious susceptible infections · 40-50 mg/kg · IV/IM/SC · q8h · Until clinical resolution · Standard recommended dose.
- Susceptible infections · 10-20 mg/kg · IV/IM/SC · q12h · Until clinical resolution · Lower dose suggested by some authors to have good clinical efficacy.
- Susceptible infections (most birds) · 50-100 mg/kg IM three times a day · IM · TID · May be used with aminoglycosides, but nephrotoxicity may occur. Reconstituted vial good for 13 weeks if frozen.
- Bacterial infections, bacterial hepatitis · 75-100 mg/kg IM or IV q4-8h · IM, IV · q4-8h
Vías de administración
Contraindicaciones
- Patients with a documented history of hypersensitivity to cephalosporins
Efectos adversos
- Pain at the IM injection site
- Thrombophlebitis (after IV administration)
- Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
- Antibiotic-associated diarrhea (alteration of gut flora)
- Sterile abscesses or local tissue reactions
- Rarely: Nephrotoxicity, neurotoxicity (at high doses), neutropenia, agranulocytosis, thrombocytopenia, hepatitis
Interacciones farmacológicas
- Aminoglycosides / Nephrotoxic drugs (e.g., amphotericin B) · Potential for additive nephrotoxicity. In vitro studies show synergistic antibacterial activity, but they must NOT be mixed in the same syringe or fluid bag.
- Probenecid · Competitively blocks the renal tubular secretion of cefotaxime, significantly increasing its serum levels and prolonging its elimination half-life.
- Oxytetracycline · Bacteriostatic agents may antagonize the bactericidal activity of cephalosporins. · moderate
- Erythromycin · Bacteriostatic agents may antagonize the bactericidal activity of cephalosporins. · moderate
- Aminoglycosides · Synergistic antibacterial effect, but do not mix in the same syringe due to chemical incompatibility. · minor
- Amphotericin B · Increased risk of nephrotoxicity. · major
- Furosemide · Loop diuretics may increase the risk of nephrotoxicity when used with cephalosporins. · major
Monitorización
- Clinical efficacy (resolution of infection signs)
- Renal function parameters (BUN, creatinine, urinalysis) in compromised patients or those on concurrent nephrotoxic drugs
Sobredosis
Acute cephalosporin overdoses are unlikely to cause significant life-threatening problems. However, massive overdoses may exacerbate adverse effects, potentially leading to **neurotoxicity** (seizures, encephalopathy), **nephrotoxicity**, or severe gastrointestinal upset. Treatment should consist of standard supportive care and monitoring.
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