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Drugs reference index «Keflex»



Generic name: Cephalexin hydrochlorideBrand names: Keftab, Keflex

Why is Keflex prescribed?

Keflex and Keftab are cephalosporin antibiotics. They are prescribed for bacterial infections of the respiratory tract, the middle ear, the bones, the skin, and the reproductive and urinary systems. Because they are effective for only certain types of bacterial infections, before beginning treatment your doctor may perform tests to identify the organisms causing the infection.

Keflex is available in capsules and an oral suspension form for use in children. Keftab, available only in tablet form, is prescribed exclusively for adults.

Most important fact about Keflex

If you are allergic to either penicillin or cephalosporin antibiotics in any form, consult your doctor before taking Keflex. There is a possibility that you are allergic to both types of medication and if a reaction occurs, it could be extremely severe. If you take the drug and feel signs of a reaction, seek medical attention immediately.

How should you take Keflex?

Keflex may be taken with or without meals. However, if the drug upsets your stomach, you may want to take it after you have eaten.

Take Keflex at even intervals around the clock as prescribed by your doctor.

If you are taking the liquid form of Keflex, use the specially marked spoon to measure each dose accurately.

Your doctor will only prescribe Keflex to treat a bacterial infection; it will not cure a viral infection, such as the common cold. It's important to take the full dosage schedule of Keflex, even if you're feeling better in a few days. Not completing the full dosage schedule may decrease the drug's effectiveness and increase the chances that the bacteria may become resistant to Keflex and similar antibiotics.

  • If you miss a dose...Take it as soon as you remember. If it is almost time for the next dose, and you take 2 doses a day, take the one you missed and the next dose 5 to 6 hours later. If you take 3 or more doses a day, take the one you missed and the next dose 2 to 4 hours later, or double the next dose. Then go back to your regular schedule.
  • Storage instructions...Store capsules and tablets at room temperature. Store the liquid suspension in a refrigerator; discard any unused medication after 14 days.

What side effects may occur?

Side effects cannot be anticipated. If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking Keflex.

  • Side effects may include:Diarrhea

Why should Keflex not be prescribed?

If you are sensitive to or have ever had an allergic reaction to the cephalosporin group of antibiotics, you should not use Keflex. Make sure your doctor is aware of any drug reactions you have experienced.

Special warnings about Keflex

If you have a history of stomach or intestinal disease, especially colitis, check with your doctor before taking Keflex.

If you have ever had an allergic reaction, particularly to drugs, be sure to tell your doctor.

If diarrhea occurs while taking cephalexin, check with your doctor before taking a remedy. Certain diarrhea medications (for instance, Lomotil) may increase your diarrhea or make it last longer.

Prolonged use of Keflex may result in an overgrowth of bacteria that do not respond to the medication, causing a secondary infection. Your doctor will monitor your use of Keflex on a regular basis.

If you have a kidney disorder, check with your doctor before taking Keflex. You may need a reduced dose.

If you are diabetic, it is important to note that Keflex may cause false results in tests for urine sugar. Notify your doctor that you are taking Keflex before being tested. Do not change your diet or dosage of diabetes medication without first consulting with your doctor.

If your symptoms do not improve within a few days, or if they get worse, notify your doctor immediately.

Do not give Keflex to other people or use it for other infections before checking with your doctor.

Possible food and drug interactions when taking Keflex

If Keflex is taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining Keflex with the following:

Certain diarrhea medications such as LomotilOral contraceptives

Special information if you are pregnant or breastfeeding

The effects of Keflex during pregnancy have not been adequately studied. If you are pregnant or plan to become pregnant, notify your doctor immediately. Keflex appears in breast milk and could affect a nursing infant. If Keflex is essential to your health, your doctor may advise you to discontinue breastfeeding until your treatment is finished.

Recommended dosage for Keflex


Throat, Skin, and Urinary Tract Infections

The usual adult dosage is 500 milligrams taken every 12 hours. Cystitis (bladder infection) therapy should be continued for 7 to 14 days.

Other Infections

The usual recommended dosage is 250 milligrams taken every 6 hours. For more severe infections, larger doses may be needed, as determined by your doctor.



The usual dose is 25 to 50 milligrams for each 2.2 pounds of body weight per day, divided into smaller doses.

For strep throat in children over 1 year of age and for skin infections, the dose may be divided into 2 doses taken every 12 hours. For strep infections, the medication should be taken for at least 10 days. Your doctor may double the dose if your child has a severe infection.

For middle ear infection, the dose is 75 to 100 milligrams per 2.2 pounds per day, divided into 4 doses.


Safety and effectiveness have not been established in children.


Any medication taken in excess can have serious consequences.

If you suspect an overdose, seek emergency medical treatment immediately.

  • Symptoms of Keflex overdose may include:Blood in the urine, diarrhea, nausea, upper abdominal pain, vomiting
  • Keflex Prescribing Information (FDA)
  • Keflex Consumer Overview
  • Keflex Advanced Consumer (Micromedex) - Includes Dosage Information
  • Keflex MedFacts Consumer Leaflet (Wolters Kluwer)
  • Cephalexin MedFacts Consumer Leaflet (Wolters Kluwer)
  • Cephalexin Prescribing Information (FDA)
  • Cephalexin Professional Patient Advice (Wolters Kluwer)
  • Panixine Prescribing Information (FDA)