Ceftazidime
Ceftazidime is a potent, injectable **third-generation cephalosporin antibiotic** primarily used to treat serious **gram-negative bacterial infections**, particularly those caused by susceptible *Enterobacteriaceae* and *Pseudomonas aeruginosa*. - **Broad Gram-Negative Spectrum:** It is often reserved for infections resistant to other, less-expensive agents or when aminoglycosides are contraindicated due to toxicity risks. - **Exotic Animal Medicine:** It is highly valued in reptile medicine due to its exceptionally long half-life in these species, allowing for infrequent dosing (e.g., every 3 days). - **Clinical Use:** Typically administered parenterally (IV, IM, or SC). Subcutaneous administration is often utilized for outpatient therapy, though it requires careful client education regarding storage and handling.
Mechanism: Ceftazidime is a **bactericidal** time-dependent antibiotic. It binds to specific **penicillin-binding proteins (PBPs)** located inside the bacterial cell wall โ inhibits the third and final stage of bacterial cell wall synthesis (peptidoglycan cross-linking) โ weakens the cell wall โ leads to cell lysis and death due to osmotic instability. *Note: While it retains some gram-positive activity from earlier generations, its primary strength is its expanded gram-negative spectrum, including antipseudomonal activity.*
Dosing by species
- Initial antibiotic therapy of gram-negative infections ยท 25 mg/kg ยท IM or SC ยท q8-12h
- Initial treatment of orthopedic infections ยท 25 mg/kg ยท IV, IM ยท q8-12h
- Initial treatment of soft tissue infections ยท 30-50 mg/kg ยท IV, IM ยท q8-12h
- Initial treatment of sepsis, bacteremia ยท 15-30 mg/kg ยท IV, IM ยท q6-8h
- Susceptible infections ยท 30 mg/kg ยท IV/IM/SC ยท q8h ยท Empirical dose; maintain tissue concentrations above MIC.
- Pseudomonas aeruginosa infections ยท 30 mg/kg ยท IV/IM/SC ยท q4h ยท Increased frequency required for Pseudomonas.
- Pseudomonas aeruginosa infections (CRI) ยท 4.4 mg/kg loading dose followed by 4.1 mg/kg/h ยท IV ยท CRI ยท Continuous rate infusion to maintain time > MIC.
- Initial treatment of systemic infections ยท 25-30 mg/kg ยท IV, IM or intraosseous ยท q8-12h
- Susceptible infections ยท 30 mg/kg ยท IM ยท q8h ยท Empirical dose.
- Pseudomonas infections ยท 30 mg/kg ยท IM ยท q2-4h ยท More frequent dosing recommended for Pseudomonas.
Routes of administration
Contraindications
- Known hypersensitivity or prior allergic reaction to cephalosporins
Adverse effects
- Pain at IM injection site (SC may be less painful)
- Gastrointestinal effects (diarrhea, vomiting)
- Hypersensitivity reactions (allergic reactions)
- Granulocytopenia
- Thrombocytopenia
- Mild azotemia
- Pseudomembranous colitis (C. difficile)
- Increased serum liver enzymes (reported in humans)
Drug interactions
- Aminoglycosides / Nephrotoxic drugs (e.g., amphotericin B) ยท Potential additive nephrotoxicity. In vitro synergy exists against certain bacteria, but they must NOT be mixed in the same syringe or fluid bag (administer separately).
- Chloramphenicol ยท May be antagonistic to ceftazidime's bactericidal effects on gram-negative bacilli; concurrent use is not recommended.
- Oxytetracycline ยท Bacteriostatic agents may antagonize the bactericidal activity of ceftazidime. ยท moderate
- Erythromycin ยท Bacteriostatic agents may antagonize the bactericidal activity of ceftazidime. ยท moderate
- Amphotericin B ยท Increased risk of nephrotoxicity when used concurrently. ยท major
- Furosemide ยท Loop diuretics may increase the risk of nephrotoxicity. ยท moderate
- Aminoglycosides ยท Synergistic in vivo against Pseudomonas; however, chemically incompatible in vitro (do not mix in the same syringe). ยท major
Monitoring
- Clinical efficacy (resolution of infection signs)
- Baseline and ongoing renal function (BUN, Creatinine, Urinalysis)
- Injection site for signs of pain or inflammation
Overdose
An acute overdose in patients with normal renal function is unlikely to be of great concern. However, in patients with **renal failure**, overdosage of ceftazidime has caused seizures, encephalopathy, coma, neuromuscular excitability, asterixis, and myoclonia. **Treatment:** Primarily symptomatic and supportive. Hemodialysis could be used to enhance elimination.
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.