Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: ampicillin
BRAND NAME: Omnipen, Polycillin, Principen
DRUG CLASS AND MECHANISM: 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 walls that surround them. The walls are necessary to protect bacteria from
their environment and to keep the contents of the bacterial cell together.
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
H. influenzae,
N. gonorrhoea,
E. coli,
Salmonella, and
Shigella,
streptococci and certain strains of
staphylococci.
Ampicillin was approved by the FDA in 1963.
PRESCRIPTION: Yes
GENERIC AVAILABLE: Yes
PREPARATIONS: Capsules: 250 and 500 mg. Powder oral suspension: 125 and 250
mg/5mL. Powder for injection: 250 mg, 500 mg, 1g, and 2 g.
STORAGE: Capsules and powder should be kept at room temperature between 15 C
(59 F) and 30 C (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.
PRESCRIBED FOR: 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
gonorrhea,
meningitis,
endocarditis and other serious infections.
DOSING: The usual oral dose range for most infections is 250 to 500 mg 4
times daily for 7-14 days. When used to treat gonorrhea, a single 3.5 gram dose
(seven 500 mg capsules) is administered with probenecid
(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 meals.
DRUG INTERACTIONS: Probenecid (Benemid) causes an increase in the amount of
ampicillin in the body. Use of ampicillin with allopurinol
(Zyloprim) can increase the
incidence of drug-related skin rash.
PREGNANCY: Ampicillin is considered safe during
pregnancy.
NURSING MOTHERS: 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.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
- amoxicillin, Amoxil, Dispermox, Trimox - Learn more about amoxicillin, including a description, generic and brand names, drug class and mechanism, preparations, storage, reasons for prescription, dosing, effect on pregnancy and nursing mothers, and common side effects.
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- Drug Interactions - Learn about potential drug interactions you may be exposed to. Drug interactions can occur with prescription drugs, OTC medication, vitamins, herbs, and supplements.
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