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Common brand names: Keflex, Biocef

Description: Cephalexin is one of the cephalosporin-type antibiotics. They are closely related to penicillin.

Dental uses: This drug is used occasionally to treat dental infections that are resistant to penicillin VK. However, most dental infections can be treated better and at less cost with penicillin VK.

Cephalexin is used in dentistry to prevent joint infections in certain patients. This includes people who have had total joint replacement surgery and are having dental procedures that are likely to cause bleeding in the mouth. Such procedures include:

  • Tooth extractions
  • Gum surgery
  • Professional cleanings
  • Orthodontic band (not bracket) placement

Another group of people also may require cephalexin. These are people who have a high risk of developing a serious heart infection called bacterial endocarditis. It can be life-threatening. People at risk for this infection need to take antibiotics before certain dental procedures. For people who are allergic to penicillins or ampicillin, cephalexin is an alternative. See important note below about allergies to penicillins and cephalosporins.

Dosages for dental purposes: The typical adult dose of cephalexin for dental infections is 250 milligrams to 1,000 milligrams every 6 hours. This should be taken for 7 to 10 days. The maximum daily dose of cephalexin is 4,000 milligrams.

The recommended dose for people at risk of joint infections is 2 grams (4 capsules of 500 milligrams each). It should be taken 1 hour before the dental procedure. The recommended dose for people at risk of endocarditis is 2 grams (4 capsules of 500 milligrams each). It should be taken 30 to 60 minutes before the procedure.

As with all medicines, follow your doctor's prescription. Take cephalexin for the prescribed length of time, even if you start to feel better. Do not stop taking it without talking to your doctor. Stopping an antibiotic too soon may cause bacteria to become resistant to antibiotics. This means the antibiotics won't work the next time.

Concerns and possible side effects: Tell your dentist and physician about all the medicines you take. This should include over-the-counter vitamins and herbal supplements. Also, let your dentist know if you have had a sensitive or allergic reaction to any medicine. If you are pregnant or nursing, or might be pregnant, talk to your primary care doctor before starting any new medicine. This also includes vitamins and supplements.

Potential side effects of cephalexin include:

  • Abdominal pain
  • Diarrhea
  • Nausea and vomiting

Studies estimate that 1% to 10% of people who are allergic to penicillins are also allergic to cephalosporins. Some people get only a mild skin rash. Some have a drop in blood pressure. In other people, the airway swells and they cannot breathe. People with a penicillin allergy should avoid cephalosporins or use them only with extreme caution.

If you take this medicine and begin to have difficulty breathing or swelling of your face, lips, tongue or throat, get medical help right away.

If you are diabetic, use Clinistix or Tes-Tape (not Clinitest) to test your urine for sugar while taking this drug. Clinitest may give a false positive reading while you are taking a cephalosporin drug.

Tell your doctor about any reaction to a prescribed medicine, no matter how minor it might be.

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