Amoxicillin is one of the most widely prescribed antibiotics in veterinary medicine and is frequently used to treat a range of bacterial infections in dogs. A broad-spectrum aminopenicillin, amoxicillin is effective against many common gram-positive and some gram-negative bacteria. It is also one of the most common “crossover” drugs — available in both human and veterinary formulations, meaning prescriptions can often be filled at regular human pharmacies. Amoxicillin requires a veterinary prescription, and proper dosing, full course completion, and appropriate case selection are essential for safe and effective use.
What Is Amoxicillin Used For?
Veterinarians prescribe amoxicillin for dogs to treat various bacterial infections, including:
- Skin infections (pyoderma) — bacterial skin infections, hot spots, and wound infections
- Urinary tract infections (UTIs) — bladder and urinary infections caused by susceptible bacteria
- Respiratory infections — bronchitis, pneumonia, and kennel cough (bacterial component)
- Dental infections — tooth abscesses and periodontal disease with bacterial involvement
- Ear infections — as a systemic antibiotic alongside topical ear treatments
- Gastrointestinal infections — certain GI bacterial infections
- Soft tissue infections — bite wounds, abscesses, and post-surgical infections
Amoxicillin is not effective against all bacteria. Your veterinarian may perform a culture and sensitivity test to confirm that the infecting bacteria are susceptible to amoxicillin before prescribing it, particularly for recurrent or non-responsive infections. Amoxicillin/clavulanate (Clavamox) may be prescribed instead when beta-lactamase-producing bacteria are suspected, as clavulanate extends the antibiotic’s effectiveness against resistant organisms.
How Does Amoxicillin Work?
Amoxicillin is a beta-lactam antibiotic that works by inhibiting bacterial cell wall synthesis. It binds to penicillin-binding proteins (PBPs) inside bacterial cells, preventing the cross-linking of peptidoglycan chains that give the cell wall its structural integrity. Without a functional cell wall, bacteria cannot maintain their shape or osmotic balance, leading to cell lysis (rupture) and death.
Amoxicillin is bactericidal, meaning it kills bacteria rather than simply inhibiting their growth. It is well absorbed after oral administration in dogs, reaching peak blood levels within one to two hours. It distributes well into most body tissues, making it effective for infections in multiple organ systems.
Dosage
Your veterinarian will determine the exact dose and duration of treatment for your dog. Never use leftover antibiotics or adjust the dose on your own.
| Dog’s Weight | Low Dose Range | High Dose Range | Frequency |
|---|---|---|---|
| 10 lbs (4.5 kg) | 50 mg | 113 mg | Every 12 hours |
| 20 lbs (9 kg) | 100 mg | 225 mg | Every 12 hours |
| 30 lbs (13.6 kg) | 150 mg | 338 mg | Every 12 hours |
| 50 lbs (22.7 kg) | 250 mg | 563 mg | Every 12 hours |
| 70 lbs (31.8 kg) | 350 mg | 788 mg | Every 12 hours |
| 100 lbs (45 kg) | 500 mg | 1125 mg | Every 12 hours |
The standard veterinary dose for dogs is 5-12 mg per pound (10-25 mg/kg) given every 12 hours. Treatment duration varies by infection type:
- Urinary tract infections: Typically 7-14 days
- Skin infections: Often 14-28 days or longer for deep pyoderma
- Respiratory infections: Usually 7-14 days
- Dental infections: Varies, often 7-10 days
Complete the full course of antibiotics as prescribed, even if your dog appears to feel better before the medication is finished. Stopping early can lead to relapse and contribute to antibiotic resistance.
How to Give Amoxicillin to Your Dog
- Amoxicillin is available as tablets, capsules, and liquid suspension (Amoxi-Drop).
- Tablets and capsules can be given with or without food. Giving with food may reduce stomach upset.
- Liquid suspension should be shaken well before each use and measured carefully with the provided dropper or syringe.
- Liquid suspension typically needs to be refrigerated after reconstitution and discarded after 14 days.
- Give doses at evenly spaced intervals (approximately every 12 hours) to maintain consistent drug levels.
- If you miss a dose, give it as soon as you remember. If the next dose is near, skip the missed dose and continue the regular schedule. Do not double up.
Side Effects
| Common Side Effects | Serious Side Effects (Contact Your Vet) |
|---|---|
| Mild GI upset (vomiting, diarrhea) | Severe or bloody diarrhea |
| Decreased appetite | Difficulty breathing or facial swelling (allergic reaction) |
| Nausea | Hives, rash, or excessive itching |
| Soft stools | Persistent vomiting |
| Drooling (if tablet has bitter taste) | Signs of secondary yeast infection |
Allergic reactions to penicillin-type antibiotics can occur in dogs, though they are less common than in humans. True anaphylactic reactions are rare but require immediate veterinary attention. GI upset is the most common side effect and is usually mild and self-limiting.
Drug Interactions
- Bacteriostatic antibiotics (doxycycline, chloramphenicol): May reduce the bactericidal effectiveness of amoxicillin if used concurrently.
- Methotrexate: Amoxicillin may reduce renal clearance of methotrexate, increasing toxicity risk.
- Probenecid: Can increase amoxicillin blood levels by slowing renal excretion.
- Warfarin/anticoagulants: May enhance anticoagulant effect.
- Other antibiotics: Your vet may intentionally combine amoxicillin with other drugs (such as metronidazole or fluoroquinolones) for broader coverage, but this should only be done under veterinary direction.
Contraindications
- Dogs with a known allergy to penicillin-type antibiotics (amoxicillin, ampicillin, or other beta-lactams)
- CRITICAL SPECIES WARNING — RABBITS: Oral amoxicillin is potentially fatal to rabbits. It can cause severe dysbiosis (disruption of normal gut bacteria) leading to fatal enterotoxemia. This applies to other oral beta-lactams, lincosamides (clindamycin), and macrolides (erythromycin) as well. Never give a dog’s amoxicillin to a rabbit, guinea pig, hamster, or chinchilla. Antibiotic selection in these species must be made by an exotics veterinarian.
- Dogs with severe kidney impairment (dose adjustment may be required)
Storage
- Tablets and capsules: Store at room temperature, 59-77degF (15-25degC), in a dry place.
- Liquid suspension (reconstituted): Refrigerate at 36-46degF (2-8degC). Shake well before use. Discard unused suspension after 14 days.
- Keep all formulations out of reach of children and pets.
Cost & Availability
Amoxicillin is one of the most affordable veterinary antibiotics, available as a generic human and veterinary medication.
- Approximate cost: $5-$25 per treatment course depending on dog size and duration
- Available at: Human pharmacies (with veterinary prescription), veterinary clinics, online pet pharmacies
- Available forms: 250 mg and 500 mg capsules; 125 mg, 250 mg, and 500 mg tablets; liquid suspension (various concentrations)
- Human formulations are therapeutically equivalent and often less expensive than veterinary-labeled products
Because amoxicillin is widely available as a generic, it is one of the most cost-effective antibiotic options for dogs.
Frequently Asked Questions
Can I use my own amoxicillin for my dog? No. Never give your dog medications from your own supply without veterinary guidance. While the active ingredient is the same, the dose, duration, and appropriateness of amoxicillin for your dog’s specific infection must be determined by a veterinarian. The wrong dose or inappropriate use can worsen the infection and contribute to antibiotic resistance.
What is the difference between amoxicillin and amoxicillin/clavulanate (Clavamox)? Amoxicillin/clavulanate (Clavamox or Augmentin) combines amoxicillin with clavulanic acid, which inhibits beta-lactamase enzymes produced by some bacteria that would otherwise destroy amoxicillin. This makes the combination effective against a wider range of bacteria, including some resistant strains. Your veterinarian will choose between the two based on the type and severity of infection.
Is amoxicillin safe for cats? Yes, amoxicillin is commonly prescribed for cats at different doses than dogs. Cats generally require lower doses. Your veterinarian will determine the appropriate dose for a cat.
Why is amoxicillin dangerous for rabbits? Rabbits (and guinea pigs, hamsters, and chinchillas) are hindgut fermenters that depend on a delicate balance of gut bacteria for digestion and survival. Oral amoxicillin and several other antibiotic classes disrupt this bacterial balance, leading to overgrowth of toxin-producing bacteria (Clostridium species), which can cause fatal enterotoxemia. Only an exotics veterinarian should prescribe antibiotics for these species.
Should I give my dog probiotics with amoxicillin? Some veterinarians recommend probiotics during antibiotic therapy to support gut health. Products like FortiFlora (Purina) or Proviable (Nutramax) are commonly recommended. Ask your veterinarian if probiotics are appropriate for your dog during antibiotic treatment.
Sources & References
- Merck Veterinary Manual - Penicillins in Animals
- VCA Hospitals - Amoxicillin
- PetMD - Amoxicillin for Dogs
- Merck Veterinary Manual - Rabbits: Antibiotic Toxicity
- FDA - Antimicrobial Resistance in Animals
- AVMA - Judicious Use of Antimicrobials
Verification Notes
Amoxicillin dosing for dogs (10-25 mg/kg every 12 hours) is consistent with standard veterinary pharmacology references and the research data compiled for this site. The rabbit enterotoxemia warning is strongly supported by the fact-check report (Claim C20: rated True, High confidence), citing MSD Vet Manual guidance that lists amoxicillin, cephalosporins, clindamycin, lincomycin, and erythromycin among antibiotics contraindicated for oral use in rabbits due to fatal dysbiosis risk. This article follows the fact-check recommendation to phrase the warning clearly: “Several antibiotic classes are high-risk in rabbits and can trigger fatal enterotoxemia.” The reminder not to share medications between species aligns with AVMA guidance that pet owners should not use any medications without veterinary direction.