Amoxicillin is probably the most prescribed antibiotic in small animal practice — and for good reason. It's broad-spectrum, well-tolerated, and cheap. But like any antibiotic, using it well matters more than using it often.

Disclaimer: This post is a general reference. Always verify dosing against your local formulary and the individual patient's clinical picture.

Standard dosage — dogs

  • Dose: 11–22 mg/kg
  • Frequency: BID (every 12 hours)
  • Route: Oral (tablet or suspension)
  • Duration: 5–14 days depending on indication

A common mid-range starting point is 15 mg/kg BID PO.

Standard dosage — cats

  • Dose: 10–20 mg/kg
  • Frequency: BID
  • Route: Oral (suspension is easier for most cats)
  • Duration: 7–14 days

Common indications

Condition Typical course
Skin infections (superficial pyoderma) 7–14 days
UTI (uncomplicated) 7–10 days
Respiratory infection (bacterial component) 7–10 days
Dental abscess (adjunctive) 5–7 days

When amoxicillin isn't enough

Amoxicillin alone doesn't cover beta-lactamase producers. For deeper or more resistant infections, you'll want amoxicillin-clavulanate (Augmentin-style) at 12.5 mg/kg BID.

Side effects to watch

  • GI upset (most common) — give with food
  • Diarrhea (uncommon but possible)
  • Allergic reactions (rare but serious) — discontinue immediately

When to avoid

  • Known penicillin allergy in the patient
  • Serious renal compromise (adjust dose)
  • Pregnancy — generally safe but discuss with client

Pro tip: let software do the math

Manually calculating 15 mg/kg for a 6.4 kg cat while a stressed owner watches is not the hill you want to die on. ClinicDesq auto-calculates dosage the moment you pick the drug — you enter the weight once, the system handles mg, ml, and tablet counts.

See how the drug calculator works →