|GENERIC NAME: Ampicillin
BRAND NAMES: Omnipen; Polycillin; Principen
DRUG CLASS AND MECHANISM: Ampicillin is one of the most widely prescribed
antibiotics. It is considered a penicillin and is a close relative of
another penicillin, amoxicillin. Unlike penicillin, ampicillin and
amoxicillin can penetrate and prevent the growth of certain types of
bacteria, called gram-negative bacteria. Ampicillin is used mainly to
treat infections of the middle ear, sinuses, bladder, kidney, and
uncomplicated gonorrhea. It also is used intravenously to treat meningitis
and other serious infections. Ampicillin was approved by the FDA in 1963.
GENERIC AVAILABLE: yes
PREPARATIONS: Tablets: 250mg; 500mg. Oral suspension: 100 mg/mL; 125
mg/5mL; 250 mg/5mL.
STORAGE: Tablets should be kept between 15°C (59°F) and 30°C (86°F). The
solution should be kept refrigerated, and can be used for up to 14 days
after it is reconstituted by the pharmacist. It must be shaken before each
use and should be kept well sealed.
PRESCRIBED FOR: Oral ampicillin (or amoxicillin) is effective against
susceptible bacteria causing infections of the middle ear, sinuses,
bladder, and kidney. Only mild to moderate infections are treated with
oral ampicillin. Bacteria against which ampicillin often is effective
include: enterococci, Listeria monocytogenes, Neisseria gonorrhoeae,
Neisseria meningitidis, some Hemophilus influenzae, Gardnerella vaginalis,
Bordetella pertussis, and some E. coli, Proteus mirabilis, Salmonella, and
Shigella. Susceptibilities of bacteria to antibiotics vary from location
to location. Thus, some doctors may use ampicillin or amoxicillin first
for some infections, whereas other doctors may use more "broad-spectrum"
DOSING: Food in the stomach reduces how much and how quickly ampicillin is
absorbed. Administration should be either 1 hour prior to or 2 hours
following a meal for maximal absorption. However, for persons who
experience nausea or stomach distress after taking ampicillin, it may be
taken with meals. Ampicillin most often is given four times a day for 7 to
14 days. When used to treat gonorrhea, it is given as a single large dose
(for example, seven 500mg capsules) with probenecid. The probenecid slows
down the elimination of the ampicillin so that the ampicillin remains in
the body longer.
DRUG INTERACTIONS: Probenecid (Benemid), causes an increase in the amount
of ampicillin in the body. This interaction may be used to advantage. (See
Dosing.) Use of ampicillin with allopurinol can increase the incidence of
drug-related skin rash. Very high doses of ampicillin (at least 1 gram or
1000 mg) can decrease the effect of atenolol (Tenormin) by decreasing its
concentration in the blood. Similarly, ampicillin, even in normal doses,
can decrease the effectiveness of birth control pills by decreasing the
blood concentrations of the estrogens in the birth control pills.
PREGNANCY: Ampicillin is considered safe during pregnancy.
NURSING MOTHERS: Ampicillin is excreted in breast milk. No side effects
have been reported in nursing infants whose mothers have taken ampicillin.
Concern for side effects such as allergic reactions, of course, exist.
Thus, physicians weigh the potential risk of allergy versus the benefits.
SIDE EFFECTS: Allergic reactions are relatively common side effects during
therapy with any of the penicillins. These reactions can range from rashes
to anaphylaxis, a severe condition in which there may be shock and even
death. Rashes occur more frequently with ampicillin than with the other
penicillins. The incidence of rash with ampicillin seems to be higher in
patients with viral illnesses, such as mononucleosis. Patients with a
history of allergic reaction to any other penicillin should not receive
ampicillin. Persons who are allergic to the cephalosporin class of
antibiotics which is more distantly related to the penicillins (e.g.,
Ceclor, Keflex, Cefzil) may or may not be allergic to penicillins.
Nausea, vomiting, loss of appetite, diarrhea, and abdominal pain are
commonly reported gastrointestinal side effects during ampicillin therapy,
but are rarely severe. Diarrhea appears to occur more frequently with
ampicillin than with the other penicillins.