Cefadroxil
Cefadroxil is a broad-spectrum, **first-generation cephalosporin** antibiotic used primarily in veterinary medicine to treat susceptible bacterial infections of the skin, soft tissue, and genitourinary tract. Structurally related to penicillins, cephalosporins contain a beta-lactam ring that confers their bactericidal activity. First-generation cephalosporins like cefadroxil are characterized by excellent activity against most **gram-positive pathogens** (including *Staphylococcus pseudintermedius*, *Staphylococcus aureus*, and *Streptococcus* spp.) and variable, limited activity against gram-negative organisms (such as *E. coli* and *Proteus mirabilis*). **Clinical Pearl:** Cefadroxil shares a nearly identical spectrum of activity with cephalexin, another common first-generation cephalosporin. However, cefadroxil has a slightly longer half-life in dogs and cats, which sometimes allows for less frequent dosing (e.g., twice daily instead of three times daily), though it is generally more expensive than generic cephalexin.
Mechanism: Cefadroxil is a **time-dependent, bactericidal** antibiotic. It exerts its effect by binding to specific **Penicillin-Binding Proteins (PBPs)** located inside the bacterial cell wall. * Binding to PBPs โ **Inhibition of peptidoglycan cross-linking** (the structural backbone of the bacterial cell wall) โ Weakening of the cell wall โ Activation of bacterial autolysins โ **Cell lysis and death**. Because it is a time-dependent antibiotic, maintaining serum drug concentrations above the Minimum Inhibitory Concentration (MIC) for the majority of the dosing interval is critical for clinical efficacy.
Dosing by species
- UTI ยท 22 mg/kg PO once daily ยท PO ยท q24h ยท 21 days or less
- Skin, pyoderma ยท 22-35 mg/kg PO q12h ยท PO ยท q12h ยท 3-30 days
- Systemic, orthopedic infections ยท 22 mg/kg PO q8-12h ยท PO ยท q8-12h ยท 30 days
- Susceptible gram-positive infections ยท 10 mg/kg q12h ยท PO ยท q12h
- Susceptible gram-negative infections ยท 30 mg/kg q8h ยท PO ยท q8h
- Susceptible infections ยท 22 mg/kg PO q12h ยท PO ยท q12h
- Susceptible infections ยท 15-20 mg/kg PO twice daily ยท PO ยท q12h
- Susceptible infections (skin, soft tissue, GU) ยท 22 mg/kg PO twice daily ยท PO ยท q12h ยท Skin/soft tissue: at least 3 days. GU: at least 7 days. Max 30 days. ยท Treat for at least 48 hours after animal is afebrile and asymptomatic. Reevaluate if no response after 3 days.
- Susceptible Staph infections ยท 30 mg/kg PO q12h ยท PO ยท q12h ยท May not be adequate dose for non-UTI's caused by E. coli.
- UTI ยท 11-22 mg/kg PO q12h ยท PO ยท q12h ยท 7-30 days
Routes of administration
Contraindications
- Known hypersensitivity to cephalosporins
- Septicemia, shock, or grave illness (oral absorption is unreliable; parenteral routes required)
Adverse effects
- Anorexia
- Vomiting
- Diarrhea
- Hypersensitivity reactions (rash, fever, eosinophilia, anaphylaxis)
- Antibiotic-associated diarrhea/superinfections
- Tachypnea (rare)
- Neurotoxicity (at high doses)
- Neutropenia/thrombocytopenia (rare, prolonged use)
- Hepatitis (rare)
- Nephrotoxicity (rare)
Drug interactions
- Probenecid ยท Competitively blocks the tubular secretion of most cephalosporins, thereby increasing serum levels and serum half-lives.
Monitoring
- Clinical efficacy (resolution of infection signs)
- Renal function (in patients with pre-existing diminished renal function)
Overdose
Acute oral cephalosporin overdoses are unlikely to cause significant problems other than **gastrointestinal distress** (vomiting, diarrhea, anorexia). Massive overdoses or prolonged use, particularly in patients with compromised kidney function, may theoretically lead to neurotoxicity, neutropenia, hepatitis, or nephrotoxicity. Treatment is generally supportive and symptomatic.
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.