Skip to Content

Generic Name: cephalexin (sef a LEX in)
Brand Names: Keflex, Panixine, Biocef, Zartan

What is Keflex?

Keflex (cephalexin) is a cephalosporin (SEF a low spor in) antibiotic. It works by fighting bacteria in your body.

Keflex is used to treat infections caused by bacteria, including upper respiratory infections, ear infections, skin infections, and urinary tract infections.

Keflex may also be used for purposes not listed in this medication guide.

Important information

You should not use Keflex if you are allergic to cephalexin or to similar antibiotics, such as Ceftin, Cefzil, Omnicef, and others. Tell your doctor if you are allergic to any drugs, especially penicillins or other antibiotics, or if you have kidney or liver disease, a stomach or intestinal disorder such as colitis, diabetes, or if you are malnourished.

Take this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Keflex will not treat a viral infection such as the common cold or flu.

Before taking this medicine

Do not use Keflex if you are allergic to cephalexin or to other cephalosporin antibiotics, such as:

  • cefaclor (Raniclor);

  • cefadroxil (Duricef);

  • cefazolin (Ancef);

  • cefdinir (Omnicef);

  • cefditoren (Spectracef);

  • cefpodoxime (Vantin);

  • cefprozil (Cefzil);

  • ceftibuten (Cedax);

  • cefuroxime (Ceftin); or

  • cephradine (Velosef), and others.

To make sure Keflex is safe for you, tell your doctor if you have:

  • an allergy to any drugs (especially penicillins);

  • kidney disease; or

  • a history of intestinal problems, such as colitis.

Keflex is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

Cephalexin can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

How should I take Keflex?

Take Keflex exactly as it was prescribed for you. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Do not use Keflex to treat any condition that has not been checked by your doctor.

Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Keflex will not treat a viral infection such as the flu or a common cold.

Do not share Keflex with another person, even if they have the same symptoms you have.

This medication can cause you to have unusual results with certain medical tests. Tell any doctor who treats you that you are using Keflex.

Store Keflex at room temperature away from moisture, heat, and light.

See also: Dosage Information (in more detail)

What happens if I miss a dose?

Take Keflex exactly as it was prescribed for you. Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea, vomiting, stomach pain, diarrhea, and blood in your urine.

What should I avoid while taking Keflex?

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, call your doctor. Do not use anti-diarrhea medicine unless your doctor tells you to.

Keflex side effects

Get emergency medical help if you have signs of an allergic reaction to Keflex: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • severe stomach pain, diarrhea that is watery or bloody;

  • jaundice (yellowing of the skin or eyes);

  • easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;

  • little or no urination;

  • agitation, confusion, hallucinations; or

  • severe skin reaction--fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Common Keflex side effects may include:

  • diarrhea;

  • dizziness, feeling tired;

  • headache, joint pain; or

  • vaginal itching or discharge.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

Keflex dosing information

Usual Adult Dose of Keflex for Bacterial Endocarditis Prophylaxis:

2 g orally as a single dose one hour before the procedure

Usual Adult Dose for Cystitis:

250 mg orally every 6 hours or 500 mg orally every 12 hours for 7 to 14 days

Usual Adult Dose for Otitis Media:

500 mg orally every 6 hours for 10 to 14 days

Usual Adult Dose for Pharyngitis:

250 mg orally every 6 hours or 500 mg orally every 12 hours

Usual Adult Dose for Skin or Soft Tissue Infection:

250 mg orally every 6 hours or 500 mg orally every 12 hours

Usual Adult Dose for Osteomyelitis:

500 mg orally every 6 hours
Therapy should be continued for approximately 4 to 6 weeks, depending on the nature and severity of the infection. Chronic osteomyelitis may require an additional one to two months of antibiotic therapy and may benefit from surgical debridement.

Usual Adult Dose for Prostatitis:

500 mg orally every 6 hours for 14 days

Usual Adult Dose for Pyelonephritis:

500 mg orally every 6 hours for 14 days

Usual Adult Dose for Upper Respiratory Tract Infection:

250 to 500 mg orally every 6 hours for 7 to 10 days

Usual Adult Dose of Keflex for Bacterial Infection:

250 to 500 mg orally every 6 hours
Therapy should be continued for approximately 7 to 21 days, depending on the nature and severity of the infection.

Usual Pediatric Dose of Keflex for Otitis Media:

12.5 to 25 mg/kg orally every 6 hours

Usual Pediatric Dose for Pharyngitis:

Over 1 year of age:
Streptococcal pharyngitis: 12.5 to 25 mg/kg orally every 12 hours

Usual Pediatric Dose for Skin or Soft Tissue Infection:

12.5 to 25 mg/kg orally every 12 hours

Usual Pediatric Dose for Bacterial Endocarditis Prophylaxis:

As an alternative in penicillin-allergic patients (non-anaphylactoid type): 50 mg/kg (maximum 2 g) orally once, 1 hour before procedure

What other drugs will affect Keflex?

Other drugs may interact with Keflex, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Where can I get more information?

  • Your pharmacist can provide more information about Keflex.
  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Keflex only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2016 Cerner Multum, Inc. Version: 8.01. Revision Date: 2016-02-04, 8:31:42 AM.

Hide