Doses - AMPICILLIN, AMPICILLIN SODIUM, AMPICILLIN TRIHYDRATE
Dogs: 
For susceptible infections: a) 10 - 20 mg/kg IV, IM, or SQ q6-8h (Vaden and Papich 1995)
b) Trihydrate injectable (Polyflex®): 5.5 - 11 mg/kg IM or SQ q8h
Sodium salt: 5.5 - 11 mg/kg IV or SQ q8h
Oral Forms: 22 - 33 mg/kg PO q8h (Aronson and Aucoin 1989)
c) For routine infections: 22 mg/kg PO tid, or 11 - 22 mg/kg IM, IV, or SQ tid-qid(Morgan 1988)
d) For susceptible UTI's: 77 mg/kg/day PO divided tid (Rogers and Lees 1989)
e) 10 - 20 mg/kg PO q6h; 5 - 10 mg/kg q6h IV, IM or SQ (Kirk 1989)
f) 10 - 55 mg/kg q6-12h PO; 5 - 11 mg/kg IV, IM, or SQ q6-12h (Greene 1984)
g) Trihydrate injectable (Polyflex®): 10 - 50 mg/kg IM or SQ q6-8h;
For beta-hemolytic Streptococcus osteomyelitis: 20 mg/kg PO q6h (Ford and Aronson1985)
Cats: 
For susceptible infections: a) 10 - 20 mg/kg IV, IM, or SQ q6-8h (Vaden and Papich 1995)
b) Trihydrate injectable (Polyflex®): 5.5 - 11 mg/kg IM or SQ q8h
Sodium salt: 5.5 - 11 mg/kg IV or SQ q8h
Oral Forms: 22 - 33 mg/kg PO q8h (Aronson and Aucoin 1989)
c) Oral: 10 - 20 mg/kg PO q8-12h (Ford and Aronson 1985)
d) For bacterial respiratory infections: 10 - 20 mg/kg PO or parenterally q8-12h(Roudebush 1985)
e) 10 - 20 mg/kg PO q6h; 5 - 10 mg/kg q6h IV, IM or SQ (Kirk 1989)
f) For routine infections: 22 mg/kg PO tid, or 11 - 22 mg/kg IM, IV, or SQ tid-qid(Morgan 1988)
g) 10 - 60 mg/kg q6-12h PO; 5 - 11 mg/kg IV, IM, or SQ q6-12h (Greene 1984)
Cattle: 
For susceptible infections: a) 4 - 10 mg/kg IM q24h (salt not indicated); 4 - 10 mg/kg PO q12-24h. (Jenkins 1986)
b) For respiratory infections: Ampicillin trihydrate (Polyflex®): 22 mg/kg SQ q12h (60 dayslaughter withdrawal suggested). (Hjerpe 1986)
c) For respiratory infections: ampicillin sodium 22 mg/kg SQ q12h;
Ampicillin trihydrate: 11 mg/kg IM q24h (Beech 1987b)
d) Ampicillin trihydrate: 15 - 22 mg/kg SQ or IM tid (Upson 1988)
Horses: 
For susceptible infections: a) Ampicillin sodium: 10 - 50 mg/kg IV or IM tid
Ampicillin trihydrate: 5 - 20 mg/kg IM bid (Robinson 1987)
b) Ampicillin sodium: 11 - 15 mg/IM or IV tid-qid (Beech 1987a)
c) Foals:Ampicillin sodium 20 mg/kg IV q6-8h (dose extrapolated from adult horses; uselonger dosage interval in premature foals or those less than 7 days of age) (Caprile and Short 1987)
d) Ampicillin trihydrate: 11 mg/kg IM q6h
Ampicillin sodium: 22 mg/kg IM q12h (Upson 1988)
e) Ampicillin sodium 22 mg/kg IM q6-12h or 25 - 100 mg/kg IV q6h.
Ampicillin trihydrate: 11 - 22 mg/kg IM q12h (Brumbaugh 1987)
Swine: 
For susceptible infections: a) Ampicillin sodium: 6 - 8 mg/kg SQ or IM q8h (Baggot 1983)
Rabbits:
For susceptible infections: a) 10 - 25 mg/kg IM or SQ q6-12h (Warning: Do not give orally to rabbits) (McConnelland Hughey 1987)
Birds: 
For susceptible infections: a) Amazon parrots: 150 - 200 mg/kg PO bid - tid (poorly absorbed PO); 100 mg/kg IM(as the trihydrate/Polyflex®) q4h.
Pet birds: 250 mg capsule in 8 oz. of drinking water (poorly absorbed; rapidly excreted)
Chickens: 1.65 g/L drinking water (see above)
Most birds: 250 mg/kg via feed for 5-10 days. Sprinkle on favorite food or add to mashor corn mix. (Clubb 1986)
b) 100 mg/kgIM or IM q8h (Hoeffer 1995)
Reptiles: 
For susceptible infections: a) Snakes: 3 - 6 mg/kg IM or SQ daily (McConnell and Hughey 1987)]
b) All species: 3 - 6 mg/kg PO, SubQ or IM every 12-24 hours for 2 weeks; not veryuseful unless used in combination with aminoglycosides. (Gauvin 1993)
Client Information - Unless otherwise instructed by the veterinarian, this drug should be givenorally on an empty stomach, at least 1 hour before feeding or 2 hours after. Keep oral suspension inthe refrigerator and discard any unused suspension after 14 days. If stored at room temperature, discard unused suspension after 7 days.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times - Veterinary-Approved Products:
Ampicillin Trihydrate Injection Powder for Suspension 10 g & 25 g (of ampicillin) vials.
Polyflex® (Fort Dodge); (Rx) Approved for use in dogs, cats, and cattle. Withdrawal times(cattle; do not treat for more than 7 days): Milk = 48 hours; Slaughter = 6 days.
Ampicillin Sodium for Injection 1 gram & 3 gram vials (of ampicillin)
Amp-Equine® (Pfizer); (Rx) Approved for use in horses not intended for food.
Human-Approved Products:
Ampicillin Sodium Powder for Injection Vials 125 mg, 250 mg, 500 mg, 1 g, 2 g, 10 g; 500 mg, 1 g, and 2 gram piggyback units; Omnipen-N® (Wyeth-Ayerst) (Rx);Polycillin-N®(Apothecon) (Rx); Totacillin-N® (SK-Beecham) (Rx); generic (Rx)Ampicillin Capsules (as either trihydrate or anhydrous) 250 mg, 500 mg; Many tradenames andgenerics; (Rx)
Ampicillin (as the trihydrate) Powder for Oral Suspension 25 mg/ml, 50 mg/ ml, 100 mg/ml in20 ml, 80 ml, 100 ml, 150 ml, and 200 ml bottles; Many tradenames; (Rx)
Also available in fixed dose combinations with:
Probenecid: Powder for Oral Suspension: 3.5 g ampicillin (as trihydrate) & 1gprobenecid/probenecid (oral): Polycillin-PRB® (Apothecon); Probampacin®, generic (Rx)
Sulbactam Sodium (injection): 1.5 g (1 g ampicillin sodium/.05 g sulbactam sodium) & 3 g (2 gampicillin sodium/1 g sulbactam sodium);Unasyn® (Roerig) (Rx)