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Cephalexin (By mouth)

Cephalexin (sef-a-LEX-in)

Treats infections. This medicine is a cephalosporin antibiotic.

Brand Name(s):

Bio-Cef, Keflex

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use this medicine if you had an allergic reaction to cephalexin or another cephalosporin medicine.

How to Use This Medicine:

Capsule, Tablet, Tablet for Suspension, Liquid

  • Take your medicine as directed.
  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.
  • You may take your medicine with food or milk to avoid stomach upset.
  • Oral liquid: Shake well just before use. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
  • Take all of the medicine in your prescription to clear up your infection, even if you feel better after the first few doses.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Capsule or tablet: Store at room temperature away from heat, moisture, and direct light.
  • Oral liquid: Store in the refrigerator for 14 days. After 14 days, throw away any unused medicine. Do not freeze.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some medicines and foods can affect how cephalexin works. Tell your doctor if you are also using
    • Metformin
    • Probenecid

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, or a history of digestive problems, such as colitis. Tell your doctor if you are allergic to penicillin.
  • This medicine can cause diarrhea. Call your doctor if the diarrhea becomes severe, does not stop, or is bloody. Do not take any medicine to stop diarrhea until you have talked to your doctor. Diarrhea can occur 2 months or more after you stop taking this medicine.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
  • Call your doctor if your symptoms do not improve or if they get worse.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, red skin rash
  • Severe diarrhea, especially if bloody or ongoing
  • Severe stomach pain, vomiting

If you notice these less serious side effects, talk with your doctor:

  • Mild diarrhea or nausea

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088


Last Updated: 12/4/2014


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