Plain-language answers about one of the most prescribed antibiotics in veterinary medicine — what it treats, the right dose by weight, what never to do, and exactly when to call your vet.
Amoxicillin is a prescription-only antibiotic in the United States. It requires a licensed veterinarian’s diagnosis and written prescription before it can legally be dispensed. The information on this page is for educational purposes only and is not veterinary medical advice. Never give your dog any antibiotic — including leftover human amoxicillin from your own medicine cabinet — without explicit veterinary direction. If your dog is sick right now, call your vet or the nearest emergency animal hospital.
Amoxicillin is one of the most frequently prescribed antibiotics in veterinary medicine, and for good reason — it is effective, affordable, and well-tolerated by most dogs when used correctly. But “commonly prescribed” does not mean “casually used.” Veterinarians and veterinary pharmacists stress that this drug must always be matched to the right infection, the right dog, and the right dose. Here is the honest, vet-sourced picture of what amoxicillin can and cannot do for your dog.
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Is amoxicillin safe for dogs? Yes — when prescribed by a vet for the correct bacterial infection at the correct dose. It is not safe when self-administered, used at the wrong dose, or given for a viral illness.Amoxicillin is a beta-lactam antibiotic in the penicillin family that has been used in veterinary medicine for decades, with a well-established safety profile. It is FDA-approved for use in dogs and cats under NADA #055-078 and #055-081 (Amoxi-Tabs, Zoetis). When dosed correctly under veterinary supervision, it is generally considered safe. However, problems arise when dosing is wrong, when it is used for non-bacterial illnesses, or when human formulations containing potentially harmful inactive ingredients such as xylitol are given without veterinary guidance.
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What infections does amoxicillin treat in dogs? Skin and soft-tissue infections, urinary tract infections (UTIs), respiratory tract infections, ear infections, and dental/oral infections caused by susceptible bacteria.Amoxicillin is a broad-spectrum antibiotic active against a wide range of gram-positive and gram-negative bacteria, including Staphylococcus, Streptococcus, Escherichia coli, and Proteus species — the organisms behind most common bacterial infections in dogs. It does not treat viral infections (like parvovirus or distemper), fungal infections, parasites, or bacteria that have developed resistance to it. A culture and sensitivity test is the gold-standard way to confirm that amoxicillin is the right antibiotic for a specific infection before prescribing it.
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What is the standard amoxicillin dose for dogs? The FDA-approved reference dose on the Amoxi-Tabs label is 5 mg per pound of body weight given by mouth twice daily — but your vet may prescribe a different dose based on your specific dog and infection type.The FDA-approved Amoxi-Tabs label (reviewed on the NIH DailyMed database) states: “The recommended dosage is 5 mg/lb of body weight twice a day.” For example, a 40-pound dog would receive approximately 200 mg by mouth twice daily. However, veterinary references including the Merck Veterinary Manual note that dosage may range from 5 to 10 mg per pound depending on the infection type, the dog’s health status, and whether kidney or liver function is impaired. Only a licensed veterinarian should calculate and prescribe the actual dose for your dog — never attempt to dose at home based on a general guideline alone.
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How long does a dog stay on amoxicillin? Most courses last 5 to 14 days, or for at least 48 hours after all symptoms have resolved — but some deep infections require longer. Always finish the full prescribed course.The FDA-approved label recommends continuing treatment for 5 to 7 days or for 48 hours after all symptoms subside. Many vets extend this to 10 to 14 days for deeper infections such as bladder infections, skin abscesses, or respiratory infections. Stopping treatment early — even when your dog appears to feel better — is one of the leading causes of antibiotic treatment failure and contributes to antimicrobial resistance, a public health concern that the FDA’s Center for Veterinary Medicine has made a strategic priority through its 2024–2028 Antimicrobial Stewardship plan.
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Can I give my dog human amoxicillin from my own medicine cabinet? No — and vets consider this one of the most dangerous mistakes pet owners make. Human formulations may contain xylitol (toxic to dogs), incorrect doses, expired ingredients, or harmful additives. A prescription is legally required.While the active ingredient in human and veterinary amoxicillin is chemically identical, the inactive ingredients, flavoring agents, preservatives, and tablet coatings can be very different. Some human amoxicillin formulations — particularly liquid suspensions marketed for children — contain xylitol, an artificial sweetener that is acutely toxic to dogs even in small amounts. Human dosing is calculated for a human’s body weight and metabolism, not a dog’s. Using the wrong dose can cause under-treatment (allowing the infection to persist and develop resistance) or overdose (causing GI damage, kidney strain, or in severe cases neurological effects).
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What are the most common side effects of amoxicillin in dogs? Vomiting, diarrhea, and decreased appetite are the most common — these usually resolve with food. Rare but serious side effects include allergic reactions including facial swelling, hives, and difficulty breathing, which require immediate veterinary care.According to VCA Animal Hospitals, gastrointestinal effects such as nausea, vomiting, and loose stool are the most frequently reported side effects and can often be minimized by giving amoxicillin with a small amount of food. Rare but serious adverse reactions include signs of allergic reaction — skin rash, hives, facial swelling, fever, difficulty breathing, and unsteadiness. Drug sensitivities can also develop over time with repeated exposure, meaning a dog that tolerated amoxicillin previously may react to it in a future course. If any signs of an allergic reaction appear, stop the medication immediately and contact your vet or an emergency clinic.
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How quickly does amoxicillin start working in dogs? The drug begins working within 1 to 2 hours of the first dose — but visible improvement in your dog’s symptoms typically takes 2 to 5 days, depending on the severity of infection.Amoxicillin is acid-stable and well-absorbed from the dog’s gastrointestinal tract after oral administration, reaching therapeutic concentrations in blood and most body tissues within one to two hours. However, the resolution of outward symptoms — reduced swelling, improved energy, decreased pain — generally takes two to five days as the bacterial load decreases. If no improvement is visible within five days of starting a correctly dosed course, the FDA-approved label advises the veterinarian to review the diagnosis and consider changing therapy. This may indicate the bacteria are resistant or that the infection is not bacterial in origin.
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What is Clavamox and when does a vet prescribe it instead of plain amoxicillin? Clavamox is amoxicillin combined with clavulanic acid — it is prescribed when an infection involves bacteria that produce beta-lactamase enzymes, making plain amoxicillin ineffective.Many bacteria protect themselves from amoxicillin by producing beta-lactamase — an enzyme that destroys the drug before it can kill the bacteria. Clavamox (amoxicillin/clavulanate) adds clavulanic acid, which blocks this enzyme defense and restores amoxicillin’s effectiveness. The Merck Veterinary Manual confirms that clavulanate-potentiated amoxicillin “markedly enhances the spectrum and efficacy against both gram-positive and gram-negative pathogens.” Vets commonly reach for Clavamox for deep skin infections, dental abscesses, bite wounds, and infections that have not responded to plain amoxicillin. The veterinary formulation uses a fixed 4:1 ratio of amoxicillin to clavulanate — different from human Augmentin ratios, making substitution inappropriate.
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Are there dogs who should NOT take amoxicillin? Yes — dogs with a known penicillin allergy must never receive amoxicillin. Dogs in shock, with a blood infection (septicemia), with severe kidney or liver disease, or who are very young or pregnant require special caution or alternative antibiotics.The FDA-approved Amoxi-Tabs label states the drug is contraindicated in dogs with a history of allergic reaction to penicillin. VCA Animal Hospitals further notes that amoxicillin should not be given by mouth to dogs in shock or with grave systemic illness, as absorption may be inadequate and the drug likely ineffective. Dogs with liver or kidney disease may experience prolonged drug effects because amoxicillin is excreted through the kidneys — your vet may reduce the dose or extend the dosing interval. If your dog has ever had a reaction to any penicillin-type antibiotic, including ampicillin, tell your vet before any new antibiotic is prescribed.
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Can amoxicillin cause antibiotic resistance in my dog? Using amoxicillin incorrectly — stopping early, using the wrong dose, or treating viral illnesses — contributes to antibiotic resistance, which the FDA identifies as a major veterinary and public health threat. Completing the full course exactly as prescribed is the most important thing you can do.The FDA’s Center for Veterinary Medicine 2024–2028 Antimicrobial Stewardship goals specifically aim to reduce resistance arising from inappropriate antibiotic use in animals. When a course of amoxicillin is stopped early or dosed incorrectly, the weakest bacteria die first but the stronger, more resistant bacteria survive, multiply, and can pass that resistance to other bacteria. This can lead to infections that no longer respond to standard antibiotics — in your dog and, in some cases, in humans sharing the household environment. Resistance can develop even when dosing is consistent, which is why culture and sensitivity testing before treatment is considered best practice for serious or recurrent infections.
Sources: Drugs.com medical answer “Is amoxicillin safe for dogs?” medically reviewed by Kristianne Hannemann PharmD, last updated Feb 25 2026 (5 mg/lb twice daily; side effects; xylitol risk; prescription required; drug interactions); FDA DailyMed Amoxi-Tabs label NADA #055-078/#055-081 Zoetis (5 mg/lb twice daily; 5–7 days or 48hr post-symptom; penicillin allergy contraindication; culture/sensitivity recommended); VCA Animal Hospitals amoxicillin monograph (vcahospitals.com — 1–2hr onset; do not use in shock/blood infection; drug sensitivities develop over time; store 59–86°F; liquid 14-day refrigerated); Merck Veterinary Manual Penicillins chapter, modified Aug 2025 (beta-lactamase resistance; clavulanate-potentiated amoxicillin efficacy; gram-positive/gram-negative spectrum); FDA CVM Antimicrobial Stewardship Goals FY 2024–2028 (fda.gov — resistance from animal antibiotic use); Single Care “amoxicillin dosage dogs” (singlecare.com — Dr. Dwight Alleyne DVM; Dr. Nita Vasudevan DVM; tablet for larger dogs, liquid for smaller/younger); GBC Health (gbchealth.org, 2026 — Clavamox 4:1 ratio; beta-lactamase defense)
Wounds, abscesses, bite wounds, hot spots
UTIs, cystitis, kidney infections
Bronchitis, pneumonia, kennel cough (secondary bacterial)
Otitis externa caused by susceptible bacteria
Dental abscesses, gum infections, post-dental surgery
Selected GI bacterial infections (vet-confirmed only)
Amoxicillin has no effect on viral infections (parvovirus, distemper, kennel cough virus, influenza), fungal infections (ringworm, yeast), parasites (fleas, ticks, worms), or bacterial strains that produce beta-lactamase enzymes. Giving amoxicillin for a viral illness does not help — it only exposes your dog to side-effect risk and contributes to antimicrobial resistance. A veterinary diagnosis is essential before any antibiotic is started.
Sources: Drugs.com amoxicillin for dogs Feb 25 2026 (skin/UTI/respiratory infections; not effective against viral, fungal, or resistant organisms); FDA DailyMed Amoxi-Tabs label (gram-positive/gram-negative spectrum including Staphylococcus, Streptococcus, E. coli, Proteus spp); VCA Animal Hospitals (ear, dental, GI use; off-label use in dogs confirmed as common veterinary practice)
The doses below are based on the FDA-approved reference dose of 5 mg per pound, given twice daily as stated on the Amoxi-Tabs label. Your veterinarian may prescribe a higher dose (up to 10 mg/lb) or a different frequency depending on the infection type, your dog’s age, and kidney or liver health. Never use this table to dose your dog without a current veterinary prescription.
| Dog Weight | Reference Dose (5 mg/lb) | Twice Daily — Total Per Day | Available Tablet Strength |
|---|---|---|---|
| Small Dogs | |||
| 10 lbs (4.5 kg) | 50 mg per dose | 100 mg/day | 50 mg tablet |
| 20 lbs (9 kg) | 100 mg per dose | 200 mg/day | 100 mg tablet |
| 25 lbs (11.3 kg) | 125 mg per dose | 250 mg/day | 100 mg + 50 mg |
| Medium Dogs | |||
| 40 lbs (18 kg) | 200 mg per dose | 400 mg/day | 200 mg tablet |
| 50 lbs (22.7 kg) | 250 mg per dose | 500 mg/day | 200 mg + 50 mg |
| 60 lbs (27 kg) | 300 mg per dose | 600 mg/day | 150 mg × 2 or 200 mg + 100 mg |
| Large Dogs | |||
| 80 lbs (36 kg) | 400 mg per dose | 800 mg/day | 400 mg tablet |
| 100 lbs (45 kg) | 500 mg per dose | 1,000 mg/day | 400 mg + 100 mg |
| Tablet Strengths Available (Amoxi-Tabs, Zoetis — FDA Approved) | |||
| 50 mg, 100 mg, 150 mg, 200 mg — bottles of 500 tablets | 400 mg — bottles of 250 tablets | ||
| Liquid suspension (Amoxi-Drops) available for small or young dogs who cannot swallow tablets — dose prescribed by vet | |||
Sources: FDA DailyMed Amoxi-Tabs label NADA #055-078 Zoetis (5 mg/lb twice daily; tablet strengths 50, 100, 150, 200, 400 mg; 5–7 day duration; 48hr post-symptom rule); Merck Veterinary Manual dosages of penicillins table accessed Feb 25 2026 (5–10 mg/lb range); Drugs.com Feb 25 2026 (40 lb dog = ~200 mg twice daily example); VCA Animal Hospitals (1–2hr onset; effects short-lived within 24hr; longer in liver/kidney disease)
Loose stool or diarrhea
Decreased appetite
Mild stomach upset
Excessive drooling
Fix: Give with food. These often resolve. Call your vet if symptoms persist beyond 24 hours or worsen.
Skin rash or welts
Difficulty breathing
Fever
Unsteadiness or weakness
Collapse or pale gums
These may signal anaphylaxis. This is a medical emergency — go to an emergency vet immediately.
Drug sensitivities to amoxicillin can develop over time with repeated exposure. Your dog may have no reaction during one course of treatment, then develop a sensitivity during a later course. This is why it is important to watch for signs of an allergic reaction over the entire length of every new course — not just the first few doses. Always tell your vet if your dog has taken amoxicillin or any penicillin-type antibiotic before, and what the outcome was.
VCA Animal Hospitals notes that amoxicillin may interact with certain urine glucose tests and cause a false positive result. If your dog is being tested for diabetes or a urinary condition while on amoxicillin, be sure to tell your veterinarian that the dog is currently taking the antibiotic so test results can be interpreted accurately.
Sources: VCA Animal Hospitals amoxicillin monograph (vcahospitals.com — side effects: skin rash, fever, facial swelling, difficulty breathing; GI upset; drug sensitivity over time; urine glucose test false positive; stop giving and contact vet immediately if serious signs); Drugs.com Feb 25 2026 (vomiting, diarrhea, decreased appetite most common; allergic reaction signs; probiotic helpful for GI issues)
Liquid suspension: Refrigerate after mixing. Discard any unused portion after 14 days — expired liquid antibiotics can lose potency or degrade into harmful compounds. Keep all medications out of reach of children and other pets.
- Every prescription medication, over-the-counter product, vitamin, supplement, or herbal remedy your dog is currently taking — even if you think it is unrelated
- Any previous allergic reaction to amoxicillin, penicillin, ampicillin, or any other antibiotic — even a mild reaction
- Any history of kidney disease, liver disease, or conditions that affect the immune system
- Whether your dog is pregnant, nursing, or intended for breeding — amoxicillin’s safety profile in pregnant dogs requires individual veterinary judgment
- All prior antibiotic treatments for the same condition, and whether they were effective — this helps the vet determine if resistance may be an issue
Sources: Drugs.com Feb 25 2026 (drug interactions: neomycin sulfate, antacids, bacteriostatic antibiotics; need complete medication list); VCA Animal Hospitals (storage: 59–86°F tablets; refrigerate liquid; discard after 14 days; keep from moisture); ASPCA/Brief Media Clavamox info sheet (vitamins and supplements may interact; pregnancy caution; prior treatment history important)
If you are certain your dog did not swallow any of the tablet, you can attempt to re-administer the same dose immediately. Common techniques vets recommend include hiding the tablet inside a small amount of peanut butter (check it contains no xylitol), a piece of cheese, a soft treat specifically made for hiding pills, or a commercial pill pocket. If you are unsure how much of the tablet was swallowed, call your vet before giving another — doubling up on doses is not safe. Never give two doses at once to make up for a missed or spit-out dose without veterinary guidance.
In general, give the missed dose as soon as you remember — unless it is close to the time of the next scheduled dose. If the next dose is due within a few hours, skip the missed dose entirely and resume the regular schedule. Never double up by giving two doses at once. Setting a phone alarm for each dose time is the simplest way to stay on schedule. Consistent timing matters because amoxicillin works by maintaining a therapeutic level in the body — gaps in the schedule allow bacteria to recover and potentially develop resistance.
No — and this is one of the most important rules of antibiotic therapy. When your dog appears to feel better, the weakest and most susceptible bacteria have been killed. The bacteria that remain are often stronger and more resistant. Stopping early allows these survivors to multiply, and the infection can return — often harder to treat than the original one. Complete the full course your veterinarian prescribed, even if your dog acts completely normal. The only exception is if your vet calls you to change or stop the treatment. The FDA’s Center for Veterinary Medicine identifies incomplete antibiotic courses as a primary driver of antimicrobial resistance in veterinary settings.
No — and veterinary pharmacists are emphatic about this. There are several reasons: First, the new illness may not be bacterial at all — using an antibiotic for a viral or fungal condition provides no benefit and creates resistance risk. Second, the bacteria causing the new infection may be a different species requiring a different antibiotic. Third, leftover amoxicillin means the original course was not completed, suggesting the original infection may not have fully resolved. Fourth, the medication may be partially degraded or improperly stored. Every course of antibiotics for your dog should begin with a veterinary examination and current prescription — not a guess from a previous illness.
Amoxicillin overdose in dogs is possible. According to the FDA-approved Clavamox/amoxicillin information sheet, vomiting is the most likely effect of a mild overdose, but large overdoses can cause serious harm including damage to the nervous system and liver. If you witness or suspect an overdose, contact your veterinarian immediately. If your vet is not available, contact one of these 24-hour pet poison control services:
- ASPCA Animal Poison Control Center: (888) 426-4435 — open 24 hours (consultation fee applies)
- Pet Poison Helpline: (855) 764-7661 — open 24 hours (consultation fee applies)
Have the medication container with you when you call — the staff will need to know the drug name, strength, and approximately how much was ingested.
Absolutely not — amoxicillin and all penicillin-type antibiotics are potentially fatal to many small pets. Rabbits, guinea pigs, chinchillas, hamsters, and gerbils have highly sensitive gastrointestinal microbiomes. Penicillin-type antibiotics can destroy the beneficial bacteria in their digestive tracts, leading to a dangerous overgrowth of Clostridium bacteria — a condition that can cause severe, often fatal enterotoxemia (gut toxicity). TotalVet and other veterinary references explicitly warn pet owners never to share a dog’s amoxicillin with small mammals. These animals require completely different antibiotics under the care of a veterinarian experienced with exotic small animals.
Yes — like all antibiotics, amoxicillin disrupts the balance of bacteria in your dog’s gastrointestinal tract, which can cause loose stool, diarrhea, or general stomach upset. Drugs.com notes that if GI symptoms are problematic, pet owners can ask their vet whether a probiotic supplement might help ease digestive side effects during the course. Veterinary-specific probiotic products designed for dogs are available at most pet stores and through your vet’s office. It is generally recommended to give probiotics at a different time of day from the antibiotic dose — separating them by at least two hours — so the antibiotic does not immediately kill the beneficial bacteria in the probiotic before they can colonize. Always ask your vet before adding any supplement during active medical treatment.
Pet Poison Helpline: (855) 764-7661
Both operate 24 hours. Consultation fee applies. For overdose, allergic reactions, or accidental ingestion of human amoxicillin.
- Give every dose at the same time each day and set a phone alarm to help you remember. Consistent timing maintains therapeutic drug levels in your dog’s body and makes the antibiotic far more effective.
- Always give with a small amount of food if your dog has a sensitive stomach — this reduces the chance of vomiting and helps ensure the full dose is absorbed and retained.
- Finish the entire prescribed course even if your dog appears completely recovered by day two or three. The bacteria that survive initial treatment are the strongest ones — stopping early lets them win.
- Watch for allergic reaction signs throughout the full course — not just the first dose. Sensitivity can develop at any point. Facial swelling, hives, or difficulty breathing require an immediate emergency vet visit.
- Safely dispose of any unused medication. Do not save leftover antibiotics for future use. The FDA recommends placing unused medications in a sealed bag with an undesirable substance (coffee grounds or cat litter) before disposal — or using an approved drug take-back program in your community.
Sources: Veterinary Medicine and Science 2023 study (4% adverse reaction rate when dosed correctly, cited in germanshepherd-pet.com Feb 2026); Drugs.com Feb 25 2026 (probiotic suggestion for GI side effects; complete course essential); FDA CVM antimicrobial stewardship 2024–2028; VCA Animal Hospitals (watch for allergic reaction entire course; drug sensitivity over time); FDA drug disposal guidance; ASPCA Animal Poison Control (888) 426-4435 (cited in Brief Media Clavamox sheet); Pet Poison Helpline (855) 764-7661 (cited in Brief Media Clavamox sheet)
- Giving human amoxicillin without veterinary guidance. Even if the active ingredient is the same, human liquid formulations may contain xylitol — which is acutely toxic to dogs. Dosing from a human prescription is almost always wrong for a dog’s body weight and metabolism. Always get a veterinary prescription for a veterinary formulation.
- Stopping the course early because the dog “seems fine.” This is the most common antibiotic mistake in both human and veterinary medicine. The drug’s job is not done when symptoms disappear — it is done when the prescribed course is complete. Stopping early selects for the most resistant bacteria and sets your dog up for a harder-to-treat relapse.
- Using leftover antibiotics for a new illness without a new diagnosis. The new illness may be viral (antibiotics won’t help), the bacteria may be a different species (amoxicillin may be wrong), or resistance may have developed from the incomplete earlier course. A fresh vet examination is always required before starting any antibiotic.
© BestiePaws.com — This guide is independently researched for educational purposes only. It is not veterinary medical advice and does not replace a licensed veterinarian’s examination, diagnosis, or prescription. All dosage information, safety guidance, and clinical details are sourced from official FDA labeling, veterinary reference publications, and peer-reviewed veterinary sources as of March 2026. Veterinary medicine evolves — always confirm current guidance with your veterinarian. Amoxicillin is a prescription drug that is illegal to administer to a dog without a valid veterinarian-client-patient relationship (VCPR). If your dog is sick, contact your veterinarian. For poisoning emergencies: ASPCA Animal Poison Control (888) 426-4435 • Pet Poison Helpline (855) 764-7661 • Both open 24 hours (consultation fee applies).
Primary sources: FDA DailyMed Amoxi-Tabs (amoxicillin tablets) USP label — NADA #055-078 / #055-081, Zoetis Inc., Revised January 2020 (accessed March 2026 via dailymed.nlm.nih.gov — approved dose 5 mg/lb twice daily; 5–7 day course; penicillin allergy contraindication; tablet strengths 50/100/150/200/400 mg; culture/sensitivity testing recommended; for dogs and cats only); Drugs.com “Is amoxicillin safe for dogs?” medically reviewed by Kristianne Hannemann PharmD, last updated Feb 25 2026 (prescription required; xylitol risk in human formulations; 5 mg/lb reference dose; GI side effects most common; drug interactions neomycin/antacids/bacteriostatic antibiotics); VCA Animal Hospitals amoxicillin monograph (vcahospitals.com — off-label use dogs/cats/ferrets; onset 1–2 hrs; short-acting within 24hr; sensitization over time; urine glucose test interference; storage 59–86°F; liquid refrigerate/14-day discard; do not use in blood infection/shock; stop and call vet for allergic signs); Merck Veterinary Manual “Use of Penicillins in Animals,” modified Aug 2025 (aminopenicillins ampicillin/amoxicillin; gram-positive/gram-negative spectrum; beta-lactamase sensitivity; clavulanate-potentiated amoxicillin efficacy; Staphylococcus/Streptococcus/E.coli/Klebsiella/Proteus susceptibility; © 2026 Merck & Co.); FDA CVM Antimicrobial Resistance page (fda.gov — 2024–2028 Stewardship Goals; Feb 12 2026 guidance finalized; resistance from incomplete courses); TotalVet (total.vet — amoxicillin not safe for rabbits/guinea pigs/hamsters; GI microbiome risk); GBC Health 2026 (Clavamox 4:1 veterinary ratio vs human Augmentin; beta-lactamase enzyme defense; long-term use yeast/resistance risk); Veterinary Medicine and Science 2023 (4% adverse reaction rate correct dosing); ASPCA Animal Poison Control (888) 426-4435; Pet Poison Helpline (855) 764-7661 (both cited per Brief Media Clavamox sheet, seattle.gov)