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Ampicillin Structural Formulae V.1.svg
Ampicillin 3d structure pdb.gif
Systematic (IUPAC) name
carboxylic acid
Clinical data
Trade names Principen, others[1]
AHFS/ monograph
MedlinePlus a685002
Licence data US FDA:link
  • A (Au), B (U.S.)
Legal status
  • UK: POM (Prescription only)
Routes of
By mouth, intravenous
Pharmacokinetic data
Bioavailability 40% (oral)
Protein binding 15 to 25%
Metabolism 12 to 50%
Biological half-life approx 1 hour
Excretion 75 to 85% renal
CAS Number 69-53-4 YesY
ATC code J01CA01 S01AA19 QJ51CA01
PubChem CID 6249
DrugBank DB00415 YesY
ChemSpider 6013 YesY
UNII 7C782967RD YesY
KEGG D00204 YesY
ChEBI CHEBI:28971 YesY
Chemical data
Formula C16H19N3O4S
Molar mass 349.41 g/mol

Ampicillin is an antibiotic used to prevent and treat a number of bacterial infections.[2] This includes respiratory tract infections, urinary tract infections, meningitis, salmonella infections, and endocarditis. It may also be used to prevent group B streptococcal infection in newborns. It is used by mouth, by injection into a muscle, or intravenously.[2] Like all antibiotics, it is not useful for the treatment of viral infections.

Common side effects include rash, nausea, and diarrhea. It should not be used in people who are allergic to penicillin. Serious side effects may include Clostridium difficile colitis or anaphylaxis. While usable in those with kidney problems the dose may need to be decreased.[2] Its use during pregnancy and breastfeeding appear to be okay.[2][3] Ampicillin was developed in 1961.[4] It is on the World Health Organization's List of Essential Medicines, the most important medication needed in a basic health system.[5] Its wholesale costs is between 0.13 and 1.20 USD for a vial of the intravenous solution as of 2014.[6] In the United States it is available as a generic medication and ten days of treatment is about 13 USD.[2]

Medical uses[edit]

It is active against many Gram-positive and Gram-negative bacteria.

Ampicillin was the first 'broad spectrum' penicillin with activity against Gram-(+) bacteria including Streptococcus pneumoniae, Streptococcus pyogenes, some isolates of Staphylococcus aureus (but not penicillin-resistant or methicillin-resistant strains), and some Enterococci. Activity against Gram-(−) bacteria includes Neisseria meningitidis, some Haemophilus influenzae, and some Enterobacteriaceae. Its spectrum of activity is enhanced by co-administration of sulbactam, a drug that inhibits beta lactamase, an enzyme produced by bacteria to inactivate ampicillin and related antibiotics.[7][8]

It is used for the treatment of infections known to be or highly likely to be caused by these bacteria. These include common respiratory infections including sinusitis, bronchitis, and pharyngitis, as well as otitis media. In combination with vancomycin (which provides coverage of ampicillin-resistant pneumococci), it is effective for the treatment of bacterial meningitis. It is also used for gastrointestinal infections caused by consuming contaminated water or food, such as Salmonella, Shigella, and Listeriosis.[9]

Ampicillin is a first-line agent for the treatment of infections caused by Enterococci. The bacteria are an important cause of healthcare-associated infections such as endocarditis, meningitis, and catheter-associated urinary tract infections that are typically resistant to other antibiotics.[9]

Side effects[edit]

Ampicillin is relatively non-toxic. Its most common side effects include rash, diarrhea, and nausea.[2] In very rare cases it causes severe side effects such as angioedema, anaphylaxis and Clostridium difficile colitis.

Mechanism of action[edit]

Ampicillin is in the penicillin group of beta-lactam antibiotics and is part of the aminopenicillin family. It is roughly equivalent to amoxicillin in terms of activity.[10]

Ampicillin is able to penetrate Gram-positive and some Gram-negative bacteria. It differs from penicillin G, or benzylpenicillin, only by the presence of an amino group. That amino group helps the drug penetrate the outer membrane of Gram-negative bacteria.

Ampicillin acts as an irreversible inhibitor of the enzyme transpeptidase, which is needed by bacteria to make their cell walls.[10] It inhibits the third and final stage of bacterial cell wall synthesis in binary fission, which ultimately leads to cell lysis; therefore ampicillin is usually bacteriolytic.[11][10]


Ampicillin has been used extensively to treat bacterial infections since 1961.[12] Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci.[11] Ampicillin (originally branded as 'Penbritin') also demonstrated activity against Gram-negative organisms such as H. influenzae, coliforms and Proteus spp.[12]


Its wholesale costs is between 0.13 and 1.20 USD for a vial of the intravenous solution as of 2014.[6] In the United States it is available as a generic medication and ten days of treatment is about 13 USD.[2]

See also[edit]


  1. ^ International trade names for Ampicillin Retrieved 14 January 2015
  2. ^ a b c d e f g "Ampicillin". The American Society of Health-System Pharmacists. Retrieved 1 August 2015. 
  3. ^ "Ampicillin use while Breastfeeding". March 2015. Retrieved 1 August 2015. 
  4. ^ Ravina, Enrique (2011). The evolution of drug discovery : from traditional medicines to modern drugs (1 ed.). Weinheim: Wiley-VCH. p. 262. ISBN 9783527326693. 
  5. ^ "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014. 
  6. ^ a b "Ampicillin". International Drug Price Indicator Guide. Retrieved 1 August 2015. 
  7. ^ Hauser AR (2013). Antibiotic Basics for Clinicians, 2nd ed. Lippincott, Williams, and Wikins, pp. 25–28
  8. ^ Akova M (January 2008). "Sulbactam-containing beta-lactamase inhibitor combinations". Clin. Microbiol. Infect. 14 Suppl 1: 185–8. doi:10.1111/j.1469-0691.2007.01847.x. PMID 18154545. 
  9. ^ a b Finberg R, Fingeroth J in Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo (eds.) (2012) Harrison's Principles of Internal Medicine, 18th ed., McGraw-Hill, Chapter 132.
  10. ^ a b c AHFS DRUG INFORMATION 2006 (2006 ed.). American Society of Health-System Pharmacists. 2006. 
  11. ^ a b Petri WA in Brunton LL, Chabner BA, Knollmann BC (eds.) (2011 ) Goodman and Gilman's The Pharmacological Basis of Therapeutics, 12th ed., Chapter 53. McGraw-Hill, New York.
  12. ^ a b Acred, P; Brown, D. M.; Turner, D. H.; Wilson, M. J. (April 1962). "Pharmacology and chemotherapy of ampicillin--a new broad-spectrum penicillin". Br J Pharmacol Chemother 18 (2): 356–69. doi:10.1111/j.1476-5381.1962.tb01416.x. PMC 1482127. PMID 13859205. 

External links[edit]