Keflex (Cephalexin)

(℞) Prescription Required

    Keflex (Cephalexin) Dosage and Side Effects

    KEFLEX is used to treat infections caused by bacteria. KEFLEX is prescribed to treat respiratory tract, middle ear, skin, bone, and urinary tract infections (UTI)It's also used to prevent infections caused by streptococcal bacteria, including prevention of rheumatic fever.

    Proper Use of this medication

    The dose of KEFLEX prescribed will depend on the type of infection and whether the person taking it is a child or an adult.

    Here are general guidelines for KEFLEX dosage:

    • The usual adult dose ranges from 1 to 4 grams a day, given in divided doses.
    • Typical adult doses of KEFLEX are 250 mg every 6 hours, or 500 mg every 12 hours.
    • The usual dose for a child is 25 to 50 milligrams (mg) per kilogram of weight, given in divided doses.
    • Keflex capsules come in 250, 333, 500, and 750 mg options.

    Doses may be doubled for more severe infections.

    Depending on the type of infection, treatment may last from 7 to 14 days.

    If very large doses of KEFLEX are needed, another type of cephalosporin that can be given by injection or an intravenous infusion may be used.

    Here are some general rules for taking KEFLEX:

    • Take it with food or milk to prevent an upset stomach.
    • Always take it as directed and for as long as directed. Skipping doses or not finishing your KEFLEX prescription can lead to a more dangerous and resistant infection.
    • Do not chew, split, or crush KEFLEX capsules. Take them whole with a full glass of water, and with food or milk.
    • Store capsules in a safe, dry place and at room temperature.
    • Keep KEFLEX suspension in the refrigerator. Don't freeze it. Unused suspension should be thrown away after 14 days.
    • If you are using KEFLEX suspension, make sure to shake the liquid well before each dose.
    • KEFLEX use may interfere with some laboratory tests. These include blood tests and some urine testing done for diabetes. Always let your caregiver know you are taking KEFLEX before you are tested.

    KEFLEX Overdose

    An overdose of KEFLEX can occur.

    Symptoms of an overdose include nausea, vomiting, stomach pain, diarrhea, and blood in the urine.

    If you think you've taken an overdose, or if someone else may have overdosed on KEFLEX, call a poison control center.

    Missed Dose of KEFLEX 

    If you miss a dose, do not double your dose.

    If you are close to your dose time, take your normal dose.

    If you are well past your dose time, wait to take a dose until the next scheduled time.

    Side Effects

    Symptoms of an allergic reaction to KEFLEX may include:

    • Rash
    • Swelling under the skin
    • Itching
    • Throat swelling
    • Wheezing
    • Difficulty breathing

    Digestive system side effects may include:

    • Diarrhea
    • Abdominal pain
    • Nausea and vomiting

    Other possible side effects of KEFLEX include vaginal discharge, headache, dizziness, aches and pains, confusion, mouth sores, and fatigue. Let your doctor know about any side effects you experience.

    Stop taking KEFLEX and call your doctor immediately if you experience:

    • Severe skin rash or swelling
    • Any trouble breathing or swallowing
    • Sudden bruising or bleeding

    Warnings and Precautions

    If you're allergic to penicillin, there's about a 10 percent chance that you will also be allergic to KEFLEX.

    You could be at higher risk for side effects from KEFLEX if you have a history of liver, kidney, or colon disease, so tell your doctor about any of these conditions as well.

    Like other antibiotics, KEFLEX may cause an overgrowth of bacteria called Clostridium difficile in your colon. Toxins produced by C. difficile can cause diarrhea and a condition called pseudomembranous colitis.

    Being on other antibiotics may also increase your risk for pseudomembranous colitis, so tell your doctor about any recent antibiotic use. 

    KEFLEX and Pregnancy

    KEFLEX should be used only if clearly needed during pregnancy, and with caution during breastfeeding.

    Tell your doctor if you are or may become pregnant or if you are breastfeeding.

    KEFLEX for Dogs

    Veterinarians often prescribe KEFLEX to dogs with bacterial infections including skin, bone, urinary tract, respiratory, and other infections.

    The drug can be given with food and is usually well-tolerated by dogs, but some may have side effects including nausea or vomiting. 

    KEFLEX should be avoided in animals that have had an allergic reaction to penicillins or other cephalosporin antibiotics. 

    Interactions with this medication

    Always tell your doctor about any medications you are taking, including other prescription drugs, over-the-counter (OTC) drugs, vitamins, dietary supplements, and herbal remedies.

    Certain drugs are known to interact with KEFLEX and may cause problems:

    KEFLEX may increase blood levels of the type 2 diabetes drug metformin. This could increase your risk for side effects.

    KEFLEX may build up in the blood when combined with the medication probenecid (Benemid, Probalan), which is used to treat gout.

    In some cases, probenecid may be used along with antibiotics to increase antibiotic strength.

    Using antibiotics may make birth control pills ineffective. A second form of contraception is recommended while you're on antibiotics.

    Other related products

    The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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