Amoxicillin/Clavulanate Potassium
Amoxicillin/Clavulanate (commonly known by the veterinary trade name **Clavamoxยฎ**) is a highly effective, broad-spectrum **potentiated aminopenicillin** antibiotic. * **Broadened Spectrum:** The addition of clavulanic acid, a beta-lactamase inhibitor, protects amoxicillin from enzymatic degradation, significantly expanding its spectrum to include many beta-lactamase-producing bacteria (e.g., *Staphylococcus* spp., *E. coli*). * **Clinical Utility:** It is FDA-approved for use in dogs and cats for urinary tract infections (UTIs), skin and soft tissue infections, and periodontal disease. * **Empiric Choice:** It is considered an excellent first-line empiric choice for bacterial cystitis in female dogs and, when combined with a fluoroquinolone, for hepatobiliary infections. * **Limitations:** It is generally **not effective** against *Pseudomonas aeruginosa* or *Enterobacter* species, which often produce type I cephalosporinases that clavulanic acid cannot inhibit.
Mechanism: **Amoxicillin** is a time-dependent, bactericidal antibiotic that binds to **Penicillin-Binding Proteins (PBPs)** โ inhibits bacterial cell wall peptidoglycan cross-linking โ compromises cell wall integrity โ cell lysis and death. **Clavulanic acid** acts as a "suicide inhibitor" by competitively and irreversibly binding to **beta-lactamase enzymes** (types II, III, IV, V, and staphylococcal penicillinases) โ prevents the enzymatic destruction of amoxicillin โ restores and expands the antimicrobial spectrum against resistant organisms. *Note: There is little synergistic activity against organisms already susceptible to amoxicillin alone.*
Dosing by species
- Susceptible infections ยท 62.5 mg/cat ยท PO ยท twice daily ยท do not exceed 30 days
- Gram-positive infections ยท 10 mg/kg ยท PO ยท twice daily
- Gram-negative infections ยท 20 mg/kg ยท PO ยท three times daily
- Susceptible UTI's ยท 62.5 mg/cat (total dose) ยท PO ยท q12h ยท 10-30 days
- Susceptible skin, soft tissue infections ยท 62.5 mg/cat (total dose) or 10-20 mg/kg ยท PO ยท q12h ยท 5-7 days
- Susceptible sepsis, pneumonia ยท 10-20 mg/kg ยท PO ยท q8h ยท 7-10 days
- Susceptible infections ยท 10-20 mg/kg ยท PO ยท 2-3 times daily
- Susceptible infections ยท 50-100 mg/kg ยท PO ยท q6-8h
- Susceptible infections (Ratites) ยท 10-15 mg/kg ยท PO ยท twice daily
- Susceptible infections ยท 13.75 mg/kg ยท PO ยท twice daily ยท do not exceed 30 days
Routes of administration
Contraindications
- Patients with a history of hypersensitivity to penicillins
- Small hindgut fermenters (rabbits, guinea pigs, chinchillas, hamsters) due to risk of fatal clostridial enterotoxemia
- Oral administration in patients with septicemia, shock, or grave illness (due to delayed/diminished GI absorption)
Adverse effects
- Gastrointestinal upset (anorexia, vomiting, diarrhea)
- Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
- Antibiotic-associated diarrhea and superinfections (due to altered gut flora)
- Neurotoxicity (e.g., ataxia in dogs) at very high doses or prolonged use
- Elevated liver enzymes (rare)
- Tachypnea, dyspnea, edema, and tachycardia (rarely reported in dogs)
Drug interactions
- Bacteriostatic Antimicrobials (e.g., chloramphenicol, macrolides, tetracyclines, sulfonamides) ยท Theoretical in vitro antagonism; clinical importance is currently in doubt but historically not recommended to combine.
- Methotrexate ยท Amoxicillin may decrease the renal excretion of methotrexate, causing increased levels and potential toxic effects.
- Probenecid ยท Competitively blocks the tubular secretion of most penicillins, thereby increasing serum levels and serum half-lives.
- Aminoglycosides ยท In vitro inactivation can occur if mixed together; serum concentrations of aminoglycosides may be falsely decreased if stored prior to analysis.
Monitoring
- Clinical efficacy (resolution of infection signs)
- Adverse gastrointestinal signs (vomiting, diarrhea, anorexia)
Overdose
Acute oral penicillin overdoses are unlikely to cause significant problems other than **gastrointestinal distress** (vomiting, diarrhea, anorexia). In humans, very high dosages of parenteral penicillins, especially in patients with underlying renal disease, have induced Central Nervous System (CNS) effects. Treatment of oral overdose should be 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.