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Ampicillin: Antibiotic Uses, Side Effects & Dosage

What is ampicillin?

Ampicillin is an antibiotic used for treating bacterial infections.

Is ampicillin available as a generic drug?


Why is ampicillin prescribed to patients?

Ampicillin is used for treating infections of the
middle ear,
sinuses, stomach
and intestines, bladder, and kidney caused by susceptible bacteria. It also is
used for treating uncomplicated
endocarditis and other serious infections. Because of the increased use of
antibiotics, many bacterial strains have become resistant to penicillins; bacteria causing serious infections should be tested for resistance against penicillins and other antibiotics.

What are the side effects of ampicillin?

Common side effects of ampicillin include:

Patients with a history of allergic reactions to other penicillins
should not receive ampicillin. Persons who are allergic to the cephalosporin
class of antibiotics, which are related to the penicillins may or may not be
allergic to penicillins [for example,
cefaclor (Ceclor),
(Keflex), and
cefprozil (Cefzil)]. Serious but rare reactions include
seizures, severe
allergic reactions (anaphylaxis),
and low platelet or red blood cell count.

Ampicillin can alter the normal
bacteria in the colon and encourage overgrowth of some bacteria such as

Clostridium difficile which causes inflammation of the colon
(pseudomembranous colitis). Patients who develop signs of pseudomembranous
colitis after starting ampicillin (diarrhea,
abdominal pain, and possibly
shock) should contact
their physician immediately.


Bowel regularity means a bowel movement every day.
See Answer

What is the dosage for ampicillin?

The usual oral dose range for most infections is 250 to 500 mg 4
times daily for 7-14 days. Injectable doses range from 250 to 2000 mg  4 times
daily. When used to treat gonorrhea, a single 3.5 gram dose (seven 500 mg
capsules) is administered with 1 g
(Benemid). The probenecid slows down the elimination of ampicillin so that
ampicillin remains in the body longer. Food in the stomach reduces how much and
how quickly ampicillin is absorbed. Therefore, ampicillin should be taken 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

Which drugs or supplements interact with ampicillin?

Probenecid (Benemid) causes an increase in the amount of
ampicillin in the body. Use of ampicillin with
(Zyloprim) can increase the incidence of drug-related
skin rash. Ampicillin
may reduce the effect BCG live  vaccine and Typhoid live vaccine .

Is ampicillin safe to use during pregnancy or while breastfeeding?

Ampicillin is considered safe during

Ampicillin is excreted in
breast milk
and may cause diarrhea
or allergic responses in nursing infants. If ampicillin is used during
pregnancy, the potential benefit of ampicillin for the mother should be weighed
against the potential risk of side effects in the infant. Ampicillin is used for
treating infants.

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What else should I know about ampicillin?

What preparations of ampicillin are available?

Capsules: 250 and 500 mg. Powder oral suspension: 125 and 250
mg/5mL. Powder for injection: 250 mg, 500 mg, 1g, and 2 g.

How should I keep ampicillin stored?

Capsules and powder should be kept at room temperature from 15 C to
30 C (59 F to 86 F). After mixing the powder with water, it can be used for up
to seven days if stored at room temperature or 14 days if refrigerated. It must
be shaken before each use and should be kept well-sealed.

How does ampicillin work?

Ampicillin belongs to a class of antibiotics called
penicillins that are used for treating bacterial infections. Other members of this class include
amoxicillin (Amoxil), piperacillin (Pipracil), ticarcillin (Ticar) and
several others. These antibiotics all have a similar mechanism of action. They
stop bacteria from multiplying by preventing bacteria from forming the cell
walls that surround them. The cell walls are necessary to protect bacteria from
their environment and to keep the contents of the bacterial cell together. Most
bacteria cannot survive without a cell wall. Penicillins are most effective when
bacteria are actively multiplying and forming cell walls. Ampicillin is
effective against many bacteria including

E. coli,

streptococci and certain strains of

When was ampicillin approved by the FDA?

Ampicillin was approved by the FDA in 1963.


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