ampicillin, Omnipen, Polycillin, Principen
Omudhome Ogbru, PharmD
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Medical and Pharmacy Editor:
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.
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.
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.
SIDE EFFECTS: Common side effects of ampicillin include nausea, vomiting, loss of appetite, diarrhea, abdominal pain, rash, itching, headache, confusion and dizziness. 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, for example, cefaclor (Ceclor), cephalexin (Keflex), and cefprozil (Cefzil), may or may not be allergic to penicillins. 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, fever, abdominal pain, and possibly shock) should contact their physician immediately.
Reference: FDA Prescribing Information
Last Editorial Review: 1/9/2009
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