cephalexin, Keflex

  • 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: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Individuals who are allergic to penicillin may also be allergic to cephalexin. Serious but rare reactions include seizures, severe allergic reactions (anaphylaxis), and low platelet or red blood cell count.

Cephalexin, like almost all antibiotics, may cause mild or severe cases of pseudomembranous colitis, a mild to severe inflammation of the colon. Antibiotics, including cephalexin alter the types of bacteria in the colon and permit overgrowth of a bacterium called Clostridium difficile. Studies indicate that toxins produced by Clostridium difficile are a primary cause of pseudomembranous colitis.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS:

  • Tablets: 250 and 500 mg.
  • Capsules: 250, 500 and 750 mg.
  • Powder for Suspension: 125 and 250 mg/5 ml.

STORAGE: Tablets and capsules should be stored at room temperature, 15 C to 30 C (59 F to 86 F). Suspensions should be refrigerated and discarded 14 days after they have been prepared from the powder.

DOSING: The dose of cephalexin for adults is 1 to 4 grams in divided doses. The usual adult dose is 250 mg every 6 hours. Some infections may be treated with 500 mg every 12 hours. Children are treated with 25-100 mg/kg/day in divided doses. The dosing interval may be every 6 or 12 hours depending on the type and seriousness of the infection.

DRUG INTERACTIONS: Cephalexin may reduce the effect of BCG and typhoid vaccines. Cephalexin should not be combined with BCG or typhoid vaccine unless there are no other options.

PREGNANCY: There are no good studies of cephalexin in pregnant women. Cephalexin should only be used during pregnancy if there are no other safe alternatives.

NURSING MOTHERS: Cephalexin is excreted in breast milk. Cephalexin should be used with caution or stopped when breastfeeding.

Medically reviewed by Omudhome Ogbru, PharmD

Reference: FDA Prescribing Information

Medically Reviewed by a Doctor on 3/27/2015

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