# Amoxicillin: veterinary dose and monograph

> Amoxicillin is a veterinary antibiotic. Time-dependent bactericidal aminopenicillin; same spectrum as ampicillin but better oral absorption in monogastrics. Indications include susceptible bacterial infections (Gram-positive and many Gram-negative); urinary tract infections; soft tissue / skin infections. This monograph lists 22 reference doses for dogs, cats, cattle, horses, pigs and birds and 5 more species, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/amoxicillin · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Antibiotic
- **Also known as:** Amoxil, Amoxi-Tabs, Amoxi-Drop, Amoxi-Mast
- **Species with doses:** Dogs, Cats, Cattle, Horses, Pigs, Birds, Ferrets, Reptiles, Hedgehogs, Sugar gliders and Primates
- **General dose range:** 10–20 mg/kg PO q12h — check the species tables for the indication
- **Routes:** PO, IV, SC, IM, Intramammary
- **Last reviewed:** 1 October 2026

## Indications

- Susceptible bacterial infections (Gram-positive and many Gram-negative)
- Urinary tract infections
- Soft tissue / skin infections
- Lyme disease (canine)
- Bovine respiratory infection
- Bovine intramammary mastitis (Amoxi-Mast)
- H. pylori eradication (with metronidazole + bismuth)

## Amoxicillin dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Amoxicillin doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Gram-positive susceptible infection | 10 mg/kg | PO | q12h | — |
| Gram-negative susceptible infection | 20 mg/kg | PO | q8h | — |
| Susceptible UTI | 10–20 mg/kg | PO | q12h | 5–7 days |
| Bacteraemia / sepsis | 22–30 mg/kg | IV | q8h | 7 days |
| Lyme disease (Borrelia burgdorferi) | 22 mg/kg | PO | q12h | 21–28 days |
| General susceptible infection (Papich) | 22 mg/kg | PO | q12h | — |

- Gram-positive susceptible infection: Plumb’s p.85 (Aucoin 2000): Gram-positive infections 10 mg/kg PO, IM or SC twice daily, continuing at least 2 days after signs resolve. Papich 5e: 22 mg/kg q12h PO (general).
- Gram-negative susceptible infection: Plumb’s p.85 (Aucoin 2000): Gram-negative infections 20 mg/kg PO three times daily (or IM/SC twice daily), continuing at least 2 days after signs resolve.
- Susceptible UTI: Plumb’s p.85 (Greene 2006): susceptible UTI 10–20 mg/kg PO q12h for 5–7 days; 11 mg/kg PO q8h (Adams 2009).
- Bacteraemia / sepsis: Plumb’s p.85 (Greene 2006): bacteraemia/sepsis 22–30 mg/kg IV, IM or SC q8h for 7 days; orthopaedic infections 22–30 mg/kg q6–8h for 7–10 days.
- Lyme disease (Borrelia burgdorferi): Plumb’s p.85 (Appel & Jacobson 1995): 22 mg/kg PO q12h for 21–28 days.
- General susceptible infection (Papich): Papich 5e: dogs and cats 22 mg/kg q12h PO.

### Cats

*Amoxicillin doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible UTI / soft tissue | 11–22 mg/kg | PO | q24h | 5–7 days |
| Sepsis / pneumonia | 10–20 mg/kg | IV | q12h | — |

- Susceptible UTI / soft tissue: Plumb’s p.86 (Greene 2006): 11–22 mg/kg PO ONCE daily for 5–7 days, or 50 mg total dose per cat once daily.
- Sepsis / pneumonia: Plumb’s p.85 (Greene 2006): sepsis 10–20 mg/kg IV, SC or PO q12h for as long as necessary. Papich 5e: 22 mg/kg q12h PO (dogs and cats).

### Cattle

*Amoxicillin doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Susceptible systemic infection | 6–10 mg/kg | SC | q24h | — | 30d slaughter |
| Respiratory infection | 11 mg/kg | IM | q12h | — | Withdrawal NOT established — treat as extra-label |
| Calves — susceptible infection (trihydrate PO) | 7 mg/kg | PO | q8–12h | — | Withdrawal NOT established — treat as extra-label |
| Subclinical mastitis (lactating dairy, Amoxi-Mast) | 62.5 mg per quarter (1 syringe) | Intramammary | per label | — | 12d slaughter / 60h milk |

- Susceptible systemic infection: Plumb’s p.85 (Jenkins 1986): 6–10 mg/kg SC or IM q24h, with a 30-day slaughter withdrawal. Papich 5e: oral amoxicillin is not recommended in ruminants (poor absorption).
- Respiratory infection: Plumb’s p.85 (Hjerpe 1986; Beech 1987): 11 mg/kg IM or SC q12h. Extra-label regimen — obtain a FARAD withdrawal.
- Calves — susceptible infection (trihydrate PO): Plumb's p.86 (Baggot 1983): amoxicillin trihydrate 7 mg/kg PO q8–12h in calves. Papich 5e: non-ruminating calves 10–22 mg/kg q8–12h PO. Obtain a FARAD withdrawal.
- Subclinical mastitis (lactating dairy, Amoxi-Mast): 62.5 mg per quarter per label.

### Horses

*Amoxicillin doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Respiratory infection (adult) | 20–30 mg/kg | PO | q6h | — |
| Foals (sodium salt) | 15–30 mg/kg | IV | q6–8h | — |

- Respiratory infection (adult): Plumb’s p.86 (Beech 1987): 20–30 mg/kg PO q6h. Papich 5e: oral amoxicillin is poorly absorbed in adult horses (well absorbed only in foals) and is not recommended by this route — prefer a parenteral beta-lactam.
- Foals (sodium salt): Plumb’s p.85 (Brumbaugh 1999): foals, amoxicillin sodium 15–30 mg/kg IV or IM q6–8h; trihydrate suspension 25–40 mg/kg PO q8h.

### Pigs

*Amoxicillin doses for pigs*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Miniature/pet pig — susceptible infection | 10–22 mg/kg | PO | q12–24h | — | Withdrawal NOT established — treat as extra-label |

- Miniature/pet pig — susceptible infection: Carpenter Exotic Animal Formulary 6th ed, Table 12-1 (p.659): miniature pigs 10–22 mg/kg PO q12–24h, or 11–13 mg/kg PO q24h. Pet pigs are legally food animals in many countries — record the treatment and obtain a withdrawal before any slaughter.

### Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

*Amoxicillin doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Susceptible systemic infection | 6–10 mg/kg | SC | q24h | — | 30d slaughter |
| Respiratory infection | 11 mg/kg | IM | q12h | — | Withdrawal NOT established — treat as extra-label |
| Calves — susceptible infection (trihydrate PO) | 7 mg/kg | PO | q8–12h | — | Withdrawal NOT established — treat as extra-label |
| Subclinical mastitis (lactating dairy, Amoxi-Mast) | 62.5 mg per quarter (1 syringe) | Intramammary | per label | — | 12d slaughter / 60h milk |

- Susceptible systemic infection: Plumb’s p.85 (Jenkins 1986): 6–10 mg/kg SC or IM q24h, with a 30-day slaughter withdrawal. Papich 5e: oral amoxicillin is not recommended in ruminants (poor absorption).
- Respiratory infection: Plumb’s p.85 (Hjerpe 1986; Beech 1987): 11 mg/kg IM or SC q12h. Extra-label regimen — obtain a FARAD withdrawal.
- Calves — susceptible infection (trihydrate PO): Plumb's p.86 (Baggot 1983): amoxicillin trihydrate 7 mg/kg PO q8–12h in calves. Papich 5e: non-ruminating calves 10–22 mg/kg q8–12h PO. Obtain a FARAD withdrawal.
- Subclinical mastitis (lactating dairy, Amoxi-Mast): 62.5 mg per quarter per label.

### Birds

*Amoxicillin doses for birds*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible infection (psittacines) | 100–125 mg/kg | PO | q8–12h | — |
| Ratites | 15–22 mg/kg | PO | q12h | — |

- Susceptible infection (psittacines): Plumb’s p.85: 125 mg/kg PO q12h, mixing the oral solution to 125 mg/mL (Antinoff 2009); 100 mg/kg q8h IM, SC or PO (Hoeffer 1995).
- Ratites: Plumb's p.86 (Jenson 1998): 15–22 mg/kg PO twice daily; or 250 mg/gallon drinking water for 3–5 days.

### Ferrets

*Amoxicillin doses for ferrets*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible infection | 10–35 mg/kg | PO | q12h | — |

- Susceptible infection: Plumb's p.86 (Williams 2000): 10–35 mg/kg PO or SC twice daily. Also used in Helicobacter mustelae triple therapy: amoxicillin 20–22 mg/kg PO q12h with metronidazole + bismuth subsalicylate.

### Reptiles

*Amoxicillin doses for reptiles*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible infection (all species) | 22 mg/kg | PO | q12–24h | — |

- Susceptible infection (all species): Plumb's p.86 (Gauvin 1993): 22 mg/kg PO q12–24h; of limited use unless combined with an aminoglycoside.

### Hedgehogs

*Amoxicillin doses for hedgehogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible infection | 15 mg/kg | PO | q12h | — |

- Susceptible infection: Carpenter Exotic Animal Formulary 6th ed, Table 8-1 (p.512): hedgehogs 15 mg/kg PO/SC/IM q12h — palatable to most hedgehogs.

### Sugar gliders

*Amoxicillin doses for sugar gliders*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible infection | 30 mg/kg | PO | q12–24h | — |

- Susceptible infection: Carpenter Exotic Animal Formulary 6th ed, Table 7-1 (p.497): sugar gliders 30 mg/kg PO/SC q12–24h.

### Primates

*Amoxicillin doses for primates*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Susceptible infection (monkeys, lemurs) | 11 mg/kg | PO | q12h | — |

- Susceptible infection (monkeys, lemurs): Carpenter Exotic Animal Formulary 6th ed, Table 13-1 (p.680): monkeys/lemurs 11 mg/kg PO or IM q12h; monkeys 6.7–13.3 mg/kg PO/IM q8h; macaques 10 mg/kg PO q12h with clarithromycin for Helicobacter pylori.

## Contraindications

Hypersensitivity to penicillins/cephalosporins. NEVER administer to rabbits, guinea pigs, chinchillas or hamsters — fatal clostridial enterotoxaemia. Avoid PO route in septic/shocky animals (use parenteral).

## Species-specific warnings

> **Caution:** Rabbits: NEVER administer ORALLY to rabbits — fatal Clostridium spiroforme enterotoxaemia within 3–10 days. Parenteral routes carry lower but still significant risk.

> **Caution:** Small mammals: NEVER orally in guinea pigs, chinchillas, hamsters, gerbils — fatal dysbiosis / Clostridium overgrowth.

> **Caution:** Horses: Caution in adult horses — risk of antibiotic-associated colitis (especially Clostridium difficile). Use only when no narrower alternative exists. Foals tolerate it better than adults.

> **Caution:** Birds: Psittacines require high doses (100–125 mg/kg PO q8–12h) due to rapid clearance — standard mammalian doses are sub-therapeutic.

> **Caution:** Cattle: Strict milk (60 h) and meat (12 d intramammary; 30 d parenteral) withdrawal periods. Verify against national authority before dairy use.

## Adverse effects

- GI: anorexia, vomiting, diarrhoea
- Hypersensitivity: rash, fever, eosinophilia, anaphylaxis
- Antibiotic-associated diarrhoea / superinfection (resistant Enterobacteriaceae)
- Rare neurotoxicity (ataxia) at very high doses or prolonged use
- Elevated liver enzymes (uncommon)

## Drug interactions

- Aminoglycosides (gentamicin, amikacin): synergistic against Enterococcus / Listeria — do NOT mix in same syringe (physical inactivation)
- Bacteriostatic antibiotics (tetracyclines, chloramphenicol, erythromycin): theoretical antagonism with concurrent use
- Probenecid: blocks renal tubular secretion of amoxicillin — prolongs half-life
- Warfarin / oral anticoagulants: may potentiate anticoagulant effect — monitor PT/INR
- Methotrexate: decreased renal clearance — toxicity risk
- Allopurinol: increased risk of rash / hypersensitivity

## Pregnancy and lactation

Generally safe — FDA Category B (human). Crosses placenta and enters milk in low concentrations. Widely used in pregnant / lactating dogs, cats, cattle. Avoid PO in lagomorphs and small mammals regardless of pregnancy.

## Monitoring

- Hypersensitivity signs (urticaria, facial oedema, anaphylaxis) — especially first dose
- Renal function (BUN / creatinine) on prolonged courses or in renal impairment
- CBC if treatment exceeds 2 weeks — rare neutropenia / thrombocytopenia
- GI tolerance — discontinue if severe diarrhoea (especially in horses)
- Culture & sensitivity at therapy start whenever feasible — empiric beta-lactam resistance is common

## Toxicity and overdose

Very wide therapeutic index — acute single-dose toxicity in monogastric mammals is rare. Chronic: GI upset (vomiting, diarrhoea), hypersensitivity (rash, fever, anaphylaxis). Rabbits / guinea pigs / chinchillas / hamsters: ORAL administration causes fatal clostridial dysbiosis even at therapeutic doses — parenteral routes safer but still risky.

Management: No specific antidote. Acute overdose: supportive — IV fluids, anti-emetic if vomiting. Anaphylaxis: epinephrine 0.01 mg/kg IM (1:1000), diphenhydramine 2–4 mg/kg IM, corticosteroid (dexamethasone 0.5 mg/kg IV), oxygen, IV fluid support.

## Clinical pearls

- Same spectrum as ampicillin but ~2× the oral bioavailability — prefer amoxicillin for PO route
- Food does not meaningfully delay absorption — give with or without meals
- For beta-lactamase producers (most Staph aureus, many E. coli, Klebsiella), pair with clavulanate (Synulox / Clavamox) or sulbactam (Amoxirum Forte)
- Cattle mastitis: Amoxi-Mast intramammary 62.5 mg per quarter per milking — strict withdrawal (60 h milk, 12 d slaughter)
- For Lyme disease in dogs: 22 mg/kg PO q12h × 21–28 days is the consensus protocol

## Mechanism of action

Beta-lactam aminopenicillin. Binds to penicillin-binding proteins (PBPs) on the bacterial cell wall, inhibiting transpeptidation and preventing peptidoglycan cross-linking — bacteriolytic, time-dependent killing. Better oral absorption and broader Gram-negative reach than ampicillin due to improved penetration of the Gram-negative outer membrane. Inactivated by bacterial beta-lactamases unless protected by clavulanate or sulbactam.

## Formulations and products

- Amoxi-Drop oral suspension 50 mg/mL
- 125 mg/5 mL human suspension
- 250 mg/5 mL human suspension
- Amoxi-Mast intramammary 62.5 mg per 10-mL syringe (Plumb’s p.87)
- Intamox 2.5 g dry-powder vial — amoxy+cloxa 1.25 g + 1.25 g (Intas; reconstitute with the supplied WFI)
- Intamox 3.5 g dry-powder vial — amoxy+cloxa 1.75 g + 1.75 g (Intas; reconstitute with the supplied WFI)
- Intamox 4.5 g dry-powder vial — amoxy+cloxa 2.25 g + 2.25 g (Intas; reconstitute with the supplied WFI)
- Amoxirum Forte 300 mg dry-powder vial — amoxy 200 mg + sulbactam 100 mg (Virbac; reconstitute per label)
- Intamox-O 1.5 g bolus (Intas, oral)
- Intamox (Intas (Neovet)) — 2.5 g (1.25 g + 1.25 g), Amoxy + Cloxa vial (parenteral)
- Intamox (Intas (Neovet)) — 3.5 g, Amoxy + Cloxa vial (parenteral)
- Intamox (Intas (Neovet)) — 4.5 g, Amoxy + Cloxa vial (parenteral)
- Intamox-O (Intas (Neovet)) — 1.5 g amoxycillin, Uncoated oral bolus
- Amoxirum Forte (Virbac) — Amoxicillin 200 mg + Sulbactam 100 mg, Vial (parenteral)
- Amoxirum Tablets (Virbac) — Amoxicillin trihydrate, Oral tablet
- Inimox Forte (Companion) (Indian Immunologicals (IIL), Hyderabad) — Amoxicillin Na 200 mg + Sulbactam Na 100 mg (300 mg per vial), Vial — IM or IV
- Inimox Forte (Livestock) (Indian Immunologicals (IIL), Hyderabad) — Amoxicillin Na 2 g + Sulbactam Na 1 g (3 g vial) or Amoxicillin Na 3 g + Sulbactam Na 1.5 g (4.5 g vial), Vial — IV, IM or Intramammary
- Moxisure-LA (Assure Biotech, Jagadhri (HR)) — 200 mg/mL (amoxycillin trihydrate 20 %), Long-acting injection
- Moxicloxa (Assure Biotech, Jagadhri (HR)) — Amoxycillin 2 g + Cloxacillin 2 g, Dry powder vial + 20 mL WFI ampoule
- Amoxil — 250 / 500 mg, Capsule (human-label)
- Mox — 125 / 250 / 500 mg, Capsule / oral suspension (human-label)
- Novamox Drops — 100 mg/mL, Paediatric oral drops (human-label)

## Storage

Tablets / capsules: 15–25 °C, dry, protected from light. Reconstituted oral suspension: refrigerate (2–8 °C), shake before use, discard after 10–14 days. Reconstituted injectable: refrigerate, use within 24 h. Intramammary syringes: store ≤25 °C.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

## Other antibiotics

- [Amikacin](https://vetmasterji.com/drugs/amikacin)
- [Amoxicillin / Clavulanic Acid](https://vetmasterji.com/drugs/amoxicillin-clavulanate)
- [Ampicillin](https://vetmasterji.com/drugs/ampicillin)
- [Apramycin](https://vetmasterji.com/drugs/apramycin)
- [Azithromycin](https://vetmasterji.com/drugs/azithromycin)
- [Cefadroxil](https://vetmasterji.com/drugs/cefadroxil)
- [Cefazolin](https://vetmasterji.com/drugs/cefazolin)
- [Cefixime](https://vetmasterji.com/drugs/cefixime)

## Frequently asked questions

### What is the dose of Amoxicillin for dogs?

Reference doses for Amoxicillin in dogs: 10 mg/kg PO q12h (Gram-positive susceptible infection); 20 mg/kg PO q8h (Gram-negative susceptible infection); 10–20 mg/kg PO q12h for 5–7 days (Susceptible UTI); 22–30 mg/kg IV q8h for 7 days (Bacteraemia / sepsis); and 2 more indication-specific doses listed on this page. Confirm against the label and the patient before use.

### What is the dose of Amoxicillin for cats?

Reference doses for Amoxicillin in cats: 11–22 mg/kg PO q24h for 5–7 days (Susceptible UTI / soft tissue); 10–20 mg/kg IV q12h (Sepsis / pneumonia). Confirm against the label and the patient before use.

### What is the dose of Amoxicillin for cattle?

Reference doses for Amoxicillin in cattle: 6–10 mg/kg SC q24h (Susceptible systemic infection); 11 mg/kg IM q12h (Respiratory infection); 7 mg/kg PO q8–12h (Calves — susceptible infection (trihydrate PO)); 62.5 mg per quarter (1 syringe) Intramammary per label (Subclinical mastitis (lactating dairy, Amoxi-Mast)). Confirm against the label and the patient before use.

### What is the withdrawal period for Amoxicillin?

Cattle, SC (Susceptible systemic infection): 30d slaughter; Cattle, IM (Respiratory infection): Withdrawal NOT established — treat as extra-label; Cattle, PO (Calves — susceptible infection (trihydrate PO)): Withdrawal NOT established — treat as extra-label; Cattle, Intramammary (Subclinical mastitis (lactating dairy, Amoxi-Mast)): 12d slaughter / 60h milk; Pigs, PO (Miniature/pet pig — susceptible infection): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Amoxicillin not be used?

Hypersensitivity to penicillins/cephalosporins. NEVER administer to rabbits, guinea pigs, chinchillas or hamsters — fatal clostridial enterotoxaemia. Avoid PO route in septic/shocky animals (use parenteral).

### What are the side effects of Amoxicillin in animals?

GI: anorexia, vomiting, diarrhoea; Hypersensitivity: rash, fever, eosinophilia, anaphylaxis; Antibiotic-associated diarrhoea / superinfection (resistant Enterobacteriaceae); Rare neurotoxicity (ataxia) at very high doses or prolonged use; Elevated liver enzymes (uncommon).

## Sources

- Plumb's Veterinary Drug Handbook
- Papich, Papich Handbook of Veterinary Drugs, 5th edition
- Carpenter, Exotic Animal Formulary

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.