Ampicillin is an antibiotic belonging to the aminopenicillin class of the penicillin family. The drug is used to prevent and treat a number of bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, salmonellosis, 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.
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. Its use during pregnancy and breastfeeding appears to be generally safe.
Ampicillin was discovered in 1958 and came into commercial use in 1961. It is on the World Health Organization's List of Essential Medicines. The World Health Organization classifies ampicillin as critically important for human medicine. It is available as a generic medication.
Medical uses
Diseases
Bacterial meningitis; an aminoglycoside can be added to increase efficacy against gram-negative meningitis bacteria Endocarditis by enterococcal strains (off-label use); often given with an aminoglycoside Gastrointestinal infections caused by contaminated water or food (for example, by Salmonella) Genito-urinary tract infections Healthcare-associated infections that are related to infections from using urinary catheters and that are unresponsive to other medications Otitis media (middle ear infection) Prophylaxis (i.e. to prevent infection) in those who previously had rheumatic heart disease or are undergoing dental procedures, vaginal hysterectomies, or C-sections. It is also used in pregnant woman who are carriers of group B streptococci to prevent early-onset neonatal infections. Respiratory infections, including bronchitis, pharyngitis Sinusitis Sepsis Whooping cough, to prevent and treat secondary infections
Ampicillin used to also be used to treat gonorrhea, but there are now too many strains resistant to penicillins.
Bacteria
Ampicillin is used to treat infections by many gram-positive and gram-negative bacteria. It was the first "broad spectrum" penicillin with activity against gram-positive bacteria, including Streptococcus pneumoniae, Streptococcus pyogenes, some isolates of Staphylococcus aureus (but not penicillin-resistant or methicillin-resistant strains), Trueperella, and some Enterococcus. It is one of the few antibiotics that works against multidrug resistant Enterococcus faecalis and E. faecium. Activity against gram-negative bacteria includes Neisseria meningitidis, some Haemophilus influenzae, and some of the Enterobacteriaceae (though most Enterobacteriaceae and Pseudomonas are resistant). 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 sometimes used in combination with other antibiotics that have different mechanisms of action, like vancomycin, linezolid, daptomycin, and tigecycline.
Available forms
Ampicillin can be administered by mouth, an intramuscular injection (shot) or by intravenous infusion. The oral form, available as capsules or oral suspensions, is not given as an initial treatment for severe infections, but rather as a follow-up to an IM or IV injection. For IV and IM injections, ampicillin is kept as a powder that must be reconstituted.
IV injections must be given slowly, as rapid IV injections can lead to convulsive seizures.
Specific populations
Ampicillin is one of the most used drugs in pregnancy, and has been found to be generally harmless both by the Food and Drug Administration in the U.S. (which classified it as category B) and the Therapeutic Goods Administration in Australia (which classified it as category A). It is the drug of choice for treating Listeria monocytogenes in pregnant women, either alone or combined with an aminoglycoside. Pregnancy increases the clearance of ampicillin by up to 50%, and a higher dose is thus needed to reach therapeutic levels.
Ampicillin crosses the placenta and remains in the amniotic fluid at 50–100% of the concentration in maternal plasma; this can lead to high concentrations of ampicillin in the newborn.
While lactating mothers secrete some ampicillin into their breast milk, the amount is minimal.
In newborns, ampicillin has a longer half-life and lower plasma protein binding. The clearance by the kidneys is lower, as kidney function has not fully developed.