Introduction

Name

• Ampicillin.

Class of drug

• Beta-lactam antimicrobial, semi-synthetic penicillin Therapeutics: beta-lactam antibacterials.

Description

Chemical name

• [2S-[2-alpha,5-alpha,6-beta(S*)]]-6-[(aminophenylacetyl)amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid.

Molecular formula

• C₁₆H₁₉N₃O₄S.

Molecular weight

• 371.4.

Physical properties

• Clear yellow aqueous solution (ampicillin sodium).
• Sterile, non-aqueous suspension (ampicillin trihydrate).

Storage requirements

• Ampicillin sodium:
  • Store dry powder at 20-25°C/68-77°F.
  • After reconstitution with sterile water for injection, USP, solution must be used within 1 h.
• Ampicillin trihydrate:
  • After reconstitution with sterile water for injection, USP, store at or below 25°C/77°F (with excursions permitted up to 30°C/86°F) for up to 3 months.

Uses

Indications

• Usually active against ß-hemolytic streptococci, enterococci and against ß-lactamase producing staphylococci, but not against methicillin (oxacillin) resistant staphylococci (MRSA) Hospital associated infections.
• In the absence of acquired resistance, E. coli and Salmonella are usually susceptible, as are some Proteus spp and Klebsiella spp.
• Although most corynebacteria are susceptible, Rhodococcus equi is usually resistant.
• Pseudomonas spp and Bacteroides spp are resistant.
• Due to expense and parenteral administration, systemic use of ampicillin sodium is typically limited to the treatment of septic foals or surgical prophylaxis.
• Appropriate first-line treatment, in conjunction with an aminoglycoside, for the treatment of neonatal sepsis.
• May used as intravenous regional perfusion or in antimicrobial impregnated beads for local treatment of musculoskeletal infections.

Administration

Pharmacokinetics

Precautions

Interactions

with other drugs

• A synergistic effect is usually described with the aminoglycosides Therapeutics: antimicrobials.
• The bactericidal activity of ampicillin may be antagonized by the concomitant use of bacteriostatic agents, eg erythromycin Erythromycin, tetracycline Therapeutics: tetracyclines).
• Probenecid reduces the excretion of cephalosporins.

Adverse Reactions

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Theelen M J P, Wilson W D, Byrne B A et al (2019) Initial antimicrobial treatment of foals with sepsis: Do our choices make a difference? Vet J 243, 74-76 PubMed.
• Winther L, Baptiste K E & Friis C (2012) Pharmacokinetics in pulmonary epithelial lining fluid and plasma of ampicillin and pivampicillin administered to horses. Res Vet Sci 92 (1), 111-115 PubMed.
• van den Hoven R, Hierweck B, Dobretsberger M, Ensink J M & Meijer L A (2003) Intramuscular dosing strategy for ampicillin sodium in horses, based on its distribution into tissue chambers before and after induction of inflammation. J Vet Pharmacol Ther 26 (6), 405-411 PubMed.

Other sources of information

• Plumb D C (2018) Plumb’s Veterinary Drug Handbook. Wiley Blackwell, USA. Online version: https://app.plumbs.com.
• Cole C, Bentz B & Maxwell L (2014) Equine Pharmacology. Wiley Blackwell, USA.
• Giguère S, Prescott J F & Dowling P M (2013) Eds Antimicrobial Therapy in Veterinary Medicine, 5th ed. Wiley Blackwell, USA.

Organisation(s)

• National Office of Animal Health (NOAH) Compendium of Data Sheets for Animal Medicines. Website: www.noahcompendium.co.uk.