Cephalexin is in a group of drugs called cephalosporin antibiotics and is used to fight bacteria in the body. It works by interfering with the bacteria"s cell wall formation, causing it to rupture, and killing the bacteria.
Cephalexin is used to treat infections caused by bacteria, including upper respiratory infections, ear infections, skin infections, and urinary tract infections.
Cephalexin may also be used for other purposes not listed in this medication guide.
Important information
Do not use this medication if you are allergic to cephalexin, or to similar antibiotics, such as Ceclor, Ceftin, Cefzil, Duricef, Fortaz, Omnicef, Spectracef, Suprax, and others.
Before using cephalexin, tell your doctor if you are allergic to any drugs (especially penicillins), 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. Cephalexin will not treat a viral infection such as the common cold or flu.
Before taking this medicine
Do not use this medication if you are allergic to cephalexin, or to other cephalosporin antibiotics, such as:
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cefaclor (Ceclor);
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cefadroxil (Duricef);
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cefdinir (Omnicef);
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cefditoren (Spectracef);
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cefixime (Suprax);
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cefprozil (Cefzil);
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ceftazidime (Fortaz); or
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cefuroxime (Ceftin).
Before using cephalexin, tell your doctor if you are allergic to any drugs (especially penicillins), or if you have:
If you have any of these conditions, you may need a dose adjustment or special tests to safely take cephalexin.
The oral suspension (liquid) form of cephalexin may contain sugar. This may affect you if you have diabetes.
FDA pregnancy category B. Cephalexin 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. Do not use this medication without telling your doctor if you are breast-feeding a baby.
See also: Pregnancy and breastfeeding warnings (in more detail)
How should I take cephalexin?
Take cephalexin exactly as it was prescribed for you. Do not use the medication in larger amounts, or use it for longer than recommended by your doctor. Follow the instructions on your prescription label.
Take cephalexin with a full glass of water.
Dissolve the cephalexin dispersible tablet in a small amount of water, about 2 teaspoonfuls. Stir this mixture and drink all of it right away. To make sure you get the entire dose, add a little more water to the same glass, swirl gently and drink right away. Do not swallow or chew a dispersible tablet.
Shake the cephalexin oral suspension (liquid) well just before you measure a dose. To be sure you get the correct dose, measure the liquid with a marked measuring spoon or medicine cup, not with a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.
Take cephalexin for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Cephalexin will not treat a viral infection such as the common cold or flu.
This medication can cause you to have unusual results with certain medical tests. Tell any doctor who treats you that you are using cephalexin.
Store the tablets and capsules at room temperature away from moisture and heat. Store the liquid medicine in the refrigerator. Throw away any unused medication after 14 days.
What happens if I miss a dose?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine.
Overdose symptoms may include nausea, vomiting, stomach pain, diarrhea, and blood in your urine.
What should I avoid?
Antibiotic medicines such as cephalexin can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or has blood in it, call your doctor. Do not use any medicine to stop the diarrhea unless your doctor has told you to.
Cephalexin side effects
Get emergency medical help if you have any of these signs of an allergic reaction to cephalexin: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have any of these serious side effects:
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diarrhea that is watery or bloody;
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seizure (convulsions);
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fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;
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pale or yellowed skin, dark colored urine, fever, confusion or weakness;
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easy bruising or bleeding, unusual weakness;
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confusion, agitation, hallucinations (seeing things that are not there); or
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urinating less than usual or not at all.
Less serious cephalexin side effects may include:
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mild nausea, vomiting, diarrhea;
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dizziness, tired feeling;
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joint pain; or
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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)
Cephalexin dosing information
Usual Adult Dose 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 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 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 cephalexin?
Before using cephalexin, tell your doctor if you are using any of the following drugs:
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a blood thinner such as warfarin (Coumadin);
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metformin (Fortamet, Glucophage, Riomet, Actoplus, Avandamet, Metaglip); or
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probenecid (Benemid).
This list is not complete and there may be other drugs that can interact with cephalexin. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.
