Amoxicillin-Clavulanate (Clavamox) in Dogs and Cats: Indications, Stewardship, and Skin and UTI Evidence

Bottom line.

• Amoxicillin-clavulanate (Clavamox) is a beta-lactam/beta-lactamase inhibitor combination active against a wide range of gram-positive, gram-negative, and anaerobic pathogens commonly isolated from skin, soft tissue, urinary tract, and dental infections in dogs and cats.
• Clavulanate extends amoxicillin's spectrum to include beta-lactamase-producing Staphylococcus, E. coli, and Pasteurella spp. — organisms commonly isolated from companion animal pyoderma and UTIs.
• For canine and feline urinary tract infections, the ISCAID 2019 guidelines recommend amoxicillin alone (not amoxicillin-clavulanate) as the preferred first empirical choice for sporadic uncomplicated cystitis, because urine amoxicillin concentrations are high enough to inhibit most susceptible organisms without clavulanate.
• Typical dose: 12.5–25 mg/kg PO q8–12h in dogs; 62.5 mg/cat PO q12h (fixed dose) or 12.5 mg/kg q12h in cats; adjust based on culture-sensitivity results and site of infection.
• Antimicrobial stewardship principles strongly favor culture and sensitivity testing before selecting amoxicillin-clavulanate empirically to avoid unnecessary broad-spectrum use.
• This is a clinician-facing evidence summary. It is not a treatment protocol; confirm drug dosing, course duration, and indication against current formularies, ISCAID guidelines, and culture sensitivity results.

Clinical facts

• Drug class: Aminopenicillin (amoxicillin) combined with a beta-lactamase inhibitor (clavulanic acid); bactericidal; inhibits cell wall synthesis.
• Spectrum: Gram-positive cocci (Staphylococcus pseudintermedius, S. aureus, Streptococcus spp.); gram-negative rods including E. coli, Pasteurella spp., Proteus mirabilis; anaerobes. Does NOT have reliable activity against Pseudomonas aeruginosa, Enterococcus spp. at labeled doses, methicillin-resistant staphylococci (MRSP/MRSA), or Klebsiella in many clinical isolates.
• FDA-approved indications (dogs and cats): Skin and soft tissue infections; urinary tract infections; periodontal/dental disease adjunct; respiratory infections in cats.
• Dosing: Dogs: 12.5–25 mg/kg PO q8–12h depending on severity and site (skin/soft tissue may be q12h; serious infections q8h). Cats: 62.5 mg/cat PO q12h (fixed) or 12.5 mg/kg q12h. Treat skin infections typically 5–7 days (superficial pyoderma minimum); deep pyoderma may require 4–8 weeks or until 2 weeks beyond clinical resolution.
• Adverse effects: GI signs (vomiting, diarrhea) most common and dose-dependent; true allergic reactions (anaphylaxis) rare but possible; diarrhea may reflect microbiome disruption.
• Administration: Give with food to reduce GI adverse effects; the clavulanate component is acid-labile and bioavailability may be modestly reduced on an empty stomach.

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What the evidence shows

ISCAID 2019 guidelines: UTI prescribing and amoxicillin-clavulanate stewardship

The 2019 International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for diagnosis and management of bacterial UTIs in dogs and cats (Weese et al., Veterinary Journal 247:8-25, 2019) are the current evidence-based standard for small animal UTI management.¹ For sporadic uncomplicated bacterial cystitis in dogs, the guidelines recommend amoxicillin (11 mg/kg PO q8h) or trimethoprim-sulfamethoxazole as preferred empirical first-line agents, with a 3–5 day treatment course. Amoxicillin-clavulanate is listed as an acceptable but not preferred initial choice — the rationale being that urine amoxicillin concentrations after standard dosing are high enough to inhibit most susceptible uropathogens, and there is little evidence that the addition of clavulanate improves outcomes for uncomplicated cystitis. The ISCAID guidelines explicitly state that evidence for the need for clavulanic acid in uncomplicated UTI is lacking. This stewardship principle is clinically important: empiric amoxicillin-clavulanate instead of amoxicillin alone unnecessarily adds a broader-spectrum inhibitor and should be reserved for cases where culture confirms beta-lactamase-producing organisms.

Skin and soft tissue infections: amoxicillin-clavulanate with documented efficacy

The most cited controlled efficacy data for amoxicillin-clavulanate in companion animal skin infections come from an experimental and clinical study by Lloyd et al. (Vet Rec, PMID 3887742) in which potentiated amoxicillin (amoxicillin-clavulanate) was compared to amoxicillin alone in experimentally induced staphylococcal skin infections in dogs and in clinical dermatological cases.² Lesions in animals treated with clavulanate-potentiated amoxicillin resolved significantly more rapidly than those treated with amoxicillin alone (P < 0.05 for both lesion diameter and inflammation score from Day 6 onward), with higher success rates particularly in cases where amoxicillin-resistant organisms were isolated. This study provides direct evidence for the clinical benefit of clavulanate potentiation in staphylococcal skin infections, where beta-lactamase production by S. pseudintermedius is common. For canine pyoderma, amoxicillin-clavulanate is an appropriate empirical choice while awaiting culture results, though MRSP resistance must be considered in refractory or recurrent cases.

Resistance trends and the case for culture-guided prescribing

Data from companion animal clinical microbiology consistently show rising resistance to amoxicillin as a single agent in canine uropathogens and skin isolates, while amoxicillin-clavulanate resistance rates remain lower — reflecting the continued beta-lactamase inhibition benefit for resistant isolates. A 10-year retrospective study (Italy, PMC12474177) found that amoxicillin resistance in canine uropathogens is the highest of any tested beta-lactam, while amoxicillin-clavulanate resistance has been significantly decreasing over recent years. This makes culture-guided selection all the more important: the choice between amoxicillin and amoxicillin-clavulanate should ideally be informed by sensitivity testing wherever practical.

How this fits clinical practice

Amoxicillin-clavulanate occupies a well-defined clinical niche: it is the appropriate beta-lactam for dogs and cats with skin, soft tissue, periodontal, or wound infections where beta-lactamase-producing organisms (S. pseudintermedius, E. coli, Pasteurella) are the likely or confirmed pathogen. For uncomplicated UTI, the ISCAID guidance is clear — start with amoxicillin alone, which achieves adequate urine concentrations for susceptible uropathogens without the stewardship cost of adding clavulanate empirically. For recurrent UTI, complicated UTI, pyelonephritis, or UTI with a culture showing beta-lactamase-positive organisms, amoxicillin-clavulanate is appropriate. The GI adverse effect (diarrhea, vomiting) is the most common clinical complaint with this combination and can be minimized by dividing the daily dose and administering with food. In cats, monitoring for GI signs is especially important given the fixed-dose tablet format (62.5 mg) and their narrower margin of tolerance for GI disruption.

Always confirm specific dose, course duration, and spectrum appropriateness against current culture-sensitivity results, ISCAID guidelines, and formulary. Antimicrobial stewardship principles mandate culture confirmation before multi-week courses in any patient.

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References

1. Weese JS, Blondeau J, Boothe D, et al. 2019. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J 247:8-25. https://www.sciencedirect.com/science/article/abs/pii/S109002331830460X
2. Lloyd DH, Lamport AI, Noble WC. 1989. Efficacy of clavulanate-potentiated amoxycillin in experimental and clinical skin infections in the dog and cat. Vet Rec 124(14):367-368. https://pubmed.ncbi.nlm.nih.gov/3887742/

Changelog

• 2026-07-02: First published.