ampicillin

  • Pharmacy Author:
    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: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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 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.

Which drugs or supplements interact with ampicillin?

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. 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 pregnancy.

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.

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 H. influenzae, N. gonorrhoea, E. coli, Salmonella, and Shigella, streptococci and certain strains of staphylococci.

When was ampicillin approved by the FDA?

Ampicillin was approved by the FDA in 1963.

Medically reviewed by Eni Williams, PharmD, PhD

REFERENCE: FDA Prescribing Information

Medically Reviewed by a Doctor on 2/6/2017

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