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 BRAND NAMES
- U.S.: Ampicillin (injection) PI
 MECHANISM OF ACTION
Ampicillin is a beta-lactam antibiotic. It acts as an irreversible inhibitor of the enzyme transpeptidase, which is needed by bacteria to make their cell walls.
Ampicillin is bactericidal at low concentrations and is clinically effective not only against the gram-positive organisms usually susceptible to penicillin G but also against a variety of gram-negative organisms.
Its spectrum of activity is enhanced by co-administration of sulbactam (See Ampicillin/Sulbactam). Sulbactam inhibits beta-lactamases, an enzyme produced by bacteria to inactivate ampicillin.
- Respiratory infections including sinusitis, bronchitis, and pharyngitis, as well as otitis media.
- Bacterial meningitis (In combination with vancomycin)
- Gastrointestinal infections caused by Salmonella, Shigella, and Listeriosis
- Infections caused by Enterococci (Gram-positive cocci) such as urinary tract infections and catheter-associated urinary tract infections, bacteremia, bacterial endocarditis, diverticulitis, and meningitis
ADULTS AND CHILDREN WEIGHING OVER 20 KG:
- For genitourinary or gastrointestinal tract infections: 500 mg four times a day
- For respiratory tract infections, the usual dose is 250 mg four times a day
CHILDREN WEIGHING 20 KG OR LESS:
- For genitourinary or gastrointestinal tract infections, the usual dose is 100 mg/kg/day total, divided in 4 doses.
- For respiratory infections, the usual dose is 50 mg/kg/day total, in equally divided and spaced doses three to four times daily.
- History of a previous hypersensitivity reaction to any of the penicillins
- Infections caused by penicillinase-producing organisms.
 PREGNANCY AND LACTATION
Pregnancy Category B (US). Ampicillin should be used during pregnancy only if clearly needed.
- Nursing Mothers: A decision should be made whether to discontinue nursing or to discontinue ampicillin, taking into account the importance of the drug to the mother.
 SIDE EFFECTS
- Common side effects include rash, diarrhea, nausea and vomiting.
- Rare and severe side effects: Anaphylaxis and Clostridium difficile diarrhea.