Cefixime
Cefixime is an oral **3rd-generation cephalosporin** antibiotic used in veterinary medicine primarily for susceptible gram-negative infections. * **Spectrum of Activity:** Highly effective against many *Enterobacteriaceae* (e.g., *Escherichia coli*, *Proteus*, *Klebsiella*) and some gram-positive organisms like *Streptococcus*. * **Limitations:** It is generally **not effective** against *Pseudomonas aeruginosa*, *Enterococcus*, *Staphylococcus*, *Bordetella*, or anaerobes. * **Clinical Utility:** Its use is typically reserved for systemic or urinary tract infections where oral treatment is desired, and when first-line agents (like fluoroquinolones or other cephalosporins) are contraindicated or ineffective. > **Clinical Pearl:** Because bacterial sensitivity to 3rd-generation cephalosporins is highly variable, culture and susceptibility testing using cefixime-specific disks or dilutions is strongly recommended before initiating therapy.
Mechanism: Cefixime is a **bactericidal** antibiotic that works by inhibiting bacterial cell wall synthesis. * Binds to specific **Penicillin-Binding Proteins (PBPs)** located inside the bacterial cell wall. * **Inhibition of transpeptidation** → prevents cross-linking of peptidoglycan chains. * **Activation of autolysins** → leads to bacterial cell wall lysis and death. It is relatively resistant to hydrolysis by many bacterial **beta-lactamases**, allowing it to remain effective against certain resistant gram-negative strains.
Dosing by species
- Susceptible infections · 5-12.5 mg/kg PO q12h · PO · q12h
- Infectious endocarditis · 10 mg/kg PO q12h · PO · q12h · Use when documented resistance against or other contraindications for fluoroquinolones and aminoglycosides exist.
- UTI · 5 mg/kg PO once to twice daily · PO · q12h or q24h · 7-14 days
- Respiratory, systemic infections · 12.5 mg/kg PO q12h · PO · q12h · 7-14 days · Duration of treatment dependent on chronicity of infection.
- Susceptible infections · 5 mg/kg PO once to twice a day · PO · q12h or q24h
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Hypersensitivity to cefixime or other cephalosporins
Adverse effects
- Gastrointestinal distress (vomiting, diarrhea)
- Hypersensitivity reactions (urticaria, pruritus, fever)
Drug interactions
- Probenecid · Competitively blocks the tubular secretion of most cephalosporins, thereby increasing serum levels and serum half-lives.
- Salicylates · May displace cefixime from plasma protein binding sites; clinical significance is unclear.
Monitoring
- Clinical efficacy (resolution of infection)
- Adverse effects (GI signs, allergic reactions)
- Renal function (in patients with pre-existing renal disease)
Overdose
Cephalosporin overdoses are generally **unlikely to cause significant problems**. * **Expected Signs:** Massive overdoses may result in gastrointestinal distress (vomiting, diarrhea) or hypersensitivity reactions. * **Management:** Treatment is largely supportive and symptomatic. Emptying the stomach may be considered for massive, recent ingestions.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.