Amoxicillin: veterinary dose and monograph

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

• 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

• 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

• 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

• 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

• 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.

• 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

• 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

• 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

• 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

• 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

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

Primates

• 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

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

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

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.

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

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

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
• Amoxicillin / Clavulanic Acid
• Ampicillin
• Apramycin
• Azithromycin
• Cefadroxil
• Cefazolin
• Cefixime

Frequently asked questions