|Systematic (IUPAC) name|
|Protein binding||15 to 25%|
|Metabolism||12 to 50%|
|Biological half-life||approx 1 hour|
|Excretion||75 to 85% renal|
|CAS Registry Number|
|ATC code||J01 S01 QJ51|
|Molecular mass||349.41 g·mol−1|
|(what is this?)|
Ampicillin is an antibiotic useful for the treatment of a number of bacterial infections. It is a beta-lactam antibiotic that is part of the aminopenicillin family and is roughly equivalent to amoxicillin in terms of activity. It is taken either orally or intravenously. It is active against many Gram-positive and Gram-negative bacteria.
It is effective for ear infections and respiratory infections such as sinusitis caused by bacteria, acute exacerbations of COPD, and epiglottitis. It is also sometimes used for the treatment of urinary tract infections, meningitis, and salmonella infections, but resistance to ampicillin is increasingly common among the bacteria responsible for these infections.
Common side effects include rash, diarrhea, nausea and vomiting. It is not useful for the treatment of viral infections.
It is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.
Ampicillin is active 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.
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.
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.
Ampicillin is relatively non-toxic. Its most common side effects include rash, diarrhea, nausea and vomiting. In very rare cases it causes severe side effects such as angioedema, anaphylaxis and Clostridium difficile diarrhea.
Mechanism of action
Belonging to the penicillin group of beta-lactam antibiotics, 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. 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 bacteriocidal.
Ampicillin has been used extensively to treat bacterial infections since 1961. 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. Ampicillin (originally branded as 'Penbritin') also demonstrated activity against Gram-negative organisms such as H. influenzae, coliforms and Proteus spp.
- Amoxycillin (p-hydroxy metabolite of ampicillin)
- Pivampicillin (special pro-drug of ampicillin)
- Azlocillin and pirbenicillin (urea and amide made from ampicillin)
- AHFS DRUG INFORMATION 2006 (2006 ed.). American Society of Health-System Pharmacists. 2006.
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