Ampicillin
Antibiotic
View Brand Names (1)Dose and dosage
For susceptible infections:
a) For Gram-positive infections: 10–20 mg/kg PO twice daily; 5 mg/kg IM, SC twice daily; 5 mg/kg IV three times daily;
For Gram-negative infections: 20–30 mg/kg PO three times daily; 10 mg/kg IM, SC three times daily; 10 mg/kg IV four times daily (Aucoin 2000)
b) For susceptible UTI’s: 20 mg/kg PO q8–12h for 7–14 days; For soft tissue infections 20–40 mg/kg PO q8–12h for 14 days; For systemic infections: 7–11 mg/kg IV, IM or SC q8–12h for as long as necessary; (Greene et al. 2006)
c) For sepsis: 20–40 mg/kg IV q6–8h (Hardie 2000)
For susceptible infections:
a) For respiratory infections: Ampicillin trihydrate: 22 mg/kg SC q12h (60 day slaughter withdrawal suggested) (Hjerpe 1986)
b) For respiratory infections: Ampicillin sodium 22 mg/kg SC q12h; Ampicillin trihydrate: 11 mg/kg IM q24h (Beech 1987b)
For susceptible infections:
a) For Gram-positive infections: 10–20 mg/kg PO twice daily; 5 mg/kg IM, SC twice daily; 5 mg/kg IV three times daily. For Gram-negative infections: 20–30 mg/kg PO three times daily; 10 mg/kg IM, SC three times daily; 10 mg/kg IV four times daily (Aucoin 2000)
b) For susceptible UTI’s: 12.5 mg/kg PO q12h for 3–7 days, 6.6 mg/kg IM or SC q12h for 3–7 days;
For susceptible soft tissue infections: 10–20 mg/kg PO, IM or SC q8h for 7 days;
For pneumonia, systemic: 22 mg/kg PO, IV or SC q8h for 7–14 days;
For meningitis, orthopedic infections: 22 mg/kg PO, IV, IM, SC q6– 8h as long as necessary;
For susceptible sepsis, bacteremia: 20–40 mg/kg IV, IM or SC q6– 8h for as long as necessary;
For neonatal sepsis: 50 mg/ kg IV or intraosseous q4–6h as long as necessary;
For susceptible orthopedic infections or meningitis: 22 mg/kg IV, IM, SC, or PO q6–8h for as long as necessary (Greene et al. 2006)
c) For sepsis: 20–40 mg/kg IV q6–8h (Hardie 2000)
d) For susceptible UTI’s: 25 mg/kg PO q8h (Polzin 2005)
e) To eliminate the leptospiremic phase of leptospirosis: 22 mg/kg q6–8h IV during the acute illness until patient is eating, then amoxicillin 22 mg/kg PO q8h (Lunn 2006)
For susceptible infections:
a) Ampicillin sodium: 10–50 mg/kg IV or IM three times daily Ampicillin trihydrate: 5–20 mg/kg IM twice daily (Robinson 1987) Ampicillin sodium: 11–15 mg/kg IM or IV three to four times daily (Beech 1987a)
b) Foals: Ampicillin sodium 11 mg/kg q6h IM or IV (Furr 1999)
c) Foals: Ampicillin sodium 15–30 mg/kg IV or IM q 6–8h (Brumbaugh 1999)
d) For intrauterine infusion: 1–3 grams. Little science is available for recommending doses, volume infused, frequency diluents, etc. Most treatments are commonly performed every day or every other day for 3–7 days.) (Perkins 1999)
For susceptible infections: 5–10 mg/kg IM, SC or IV twice daily (Williams 2000)
Not recommended as it can cause a fatal enteritis (Ivey & Morrisey 2000)
a) Gerbils, Mice, Rats: 20–100 mg/kg PO, SC, IM q8–12h
b) Guinea pigs, Chinchillas, Hamsters: Do NOT use as it may cause enterocolitis (Adamcak & Otten 2000)
c) Hedgehogs: 10 mg/kg IM or PO once daily (Smith 2000)
For susceptible infections:
a) Ampicillin sodium: 6–8 mg/kg SC or IM q8h (Baggot 1983)
For susceptible infections:
a) Amazon parrots: 150–200 mg/kg PO twice daily–three times daily (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 mash or corn mix. (Clubb 1986)
b) 100 mg/kg IM or IM q8h (Hoeffer 1995)
c) Ratites: 11–15 mg/kg PO or IV 3 times daily; 15–20 mg/kg IM twice daily (Jenson 1998)
For susceptible infections:
a) All species: 3–6 mg/kg PO, SC or IM every 12–24 hours for 2 weeks; not very useful unless used in combination with aminoglycosides (Gauvin 1993)
b) For Chelonians (turtles et al): 50 mg/kg IM q12h (Jacobson 2000)
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Ampicillin is indicated in patients with infections caused by susceptible bacteria, such as skin and soft tissue infections, UTIs, and pneumonia. Gram-positive bacteria (except beta-lactamase– producing strains of Staphylococcus spp.) are usually susceptible. However, infections caused by most gram-negative bacteria of the Enterobacteriaceae are clinically resistant. Fastidious gram-negative bacteria (e.g., Pasteurella) are usually clinically susceptible.
Use cautiously in animals allergic to penicillin-like drugs.
Beta-lactam antibiotic. Ampicillin inhibits bacterial cell wall synthesis. Ampicillin has a narrow spectrum of activity that is similar to that of amoxicillin. Ampicillin spectrum of activity includes streptococci, non–beta-lactamase– producing staphylococci, and other gram-positive cocci and bacilli. Many staphylococci are resistant because of beta-lactamase production. Most enteric gram-negative bacilli of the Enterobacteriaceae are clinically resistant. Susceptible gram-negative bacteria include some species of Proteus spp., Pasteurella multocida, and Histophilus spp.
BACTERIOSTATIC ANTIMICROBIALS (e.g., chloramphenicol, erythromycin and other macrolides, tetracyclines, sulfonamides, etc.): Because there is evidence of in vitro antagonism between beta-lactam antibiotics and bacteriostatic antibiotics, use together has not been generally recommended in the past, but actual clinical importance is not clear and currently in doubt.
METHOTREXATE: Ampicillin may decrease the renal excretion of MTX causing increased levels and potential toxic effects
PROBENECID: Competitively blocks the tubular secretion of most penicillins thereby increasing serum levels and serum half-lives
Adverse effects of penicillin drugs are most commonly caused by drug allergy. This can range from acute anaphylaxis when administered IV to other signs of allergic reaction when other routes are used. When used for prophylaxis during surgery, ampicillin can be administered IV to anesthetized patients without affecting cardiovascular parameters. Diarrhea is possible when administered orally, especially with high doses
Acute oral penicillin overdoses are unlikely to cause significant problems other than GI distress, but other effects are possible (see Adverse Effects). In humans, very high dosages of parenteral penicillins, particularly in patients with renal disease, have induced CNS effects.
Penicillins have been shown to cross the placenta; safe use during pregnancy has not been firmly established, but neither have there been any documented teratogenic problems associated with these drugs. However, use only when the potential benefits outweigh the risks.
Rapid IV bolus injection can produce CNS excitement and convulsive seizures.