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Keflex Side Effects Center
Pharmacy Editor: Eni Williams, PharmD
Keflex (cephalexin) is a medication that belongs to a drug class, cephalosporin antibiotics. It is available as a generic drug and is prescribed to treat bacterial infections. It is also used before dental procedures in patients identified with certain heart-related conditions to prevent bacterial infections of the heart known as endocarditis. Common side effects include: diarrhea, dizziness, headache, stomach upset, abdominal pain, nausea/vomiting, itching/swelling and rash.
Keflex dosage depends on the condition being treated. Keflex should be used with caution in patients who have kidney disease and those who report a history of penicillin allergy. There have not been adequate studies in pregnant women, so Keflex should be used in pregnancy only when it is absolutely needed. Keflex is found in breast milk and should be used with caution in breastfeeding women.
Our Keflex (cephalexin) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
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.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Keflex in Detail - Patient Information: Side Effects
Get emergency medical help if you have any of these signs of an allergic reaction: 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:
- diarrhea that is watery or bloody;
- seizure (convulsions);
- fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;
- pale or yellowed skin, dark colored urine, fever, confusion or weakness;
- easy bruising or bleeding, unusual weakness;
- confusion, agitation, hallucinations (seeing things that are not there); or
- urinating less than usual or not at all.
Less serious side effects may include:
- mild nausea, vomiting, diarrhea;
- dizziness, tired feeling;
- 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. You may report side effects to FDA at 1-800-FDA-1088.
Read the entire detailed patient monograph for Keflex (Cephalexin) »
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Keflex Overview - Patient Information: Side Effects
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.
This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to a resistant bacteria. This condition may occur during treatment or weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have any of the following symptoms because these products may make them worse. Tell your doctor right away if you develop: persistent diarrhea, abdominal or stomach pain/cramping, blood/mucus in your stool.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Keflex (Cephalexin)»
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Keflex FDA Prescribing Information: Side Effects
Gastrointestinal - Onset of pseudomembranous colitis may occur during or after antibacterial treatment. (see WARNINGS.) Nausea and vomiting have been reported rarely. The most frequent side effect has been diarrhea. It was very rarely severe enough to warrant cessation of therapy. Dyspepsia, gastritis, and abdominal pain have also occurred. As with some penicillins and some other cephalosporins, transient hepatitis and cholestatic jaundice have been reported rarely.
Hypersensitivity - Allergic reactions in the form of rash, urticaria, angioedema, and, rarely, erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis have been observed. These reactions usually subsided upon discontinuation of the drug. In some of these reactions, supportive therapy may be necessary. Anaphylaxis has also been reported.
Other reactions have included genital and anal pruritus, genital moniliasis, vaginitis and vaginal discharge, dizziness, fatigue, headache, agitation, confusion, hallucinations, arthralgia, arthritis, and joint disorder. Reversible interstitial nephritis has been reported rarely. Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia, and slight elevations in AST and ALT have been reported.
In addition to the adverse reactions listed above that have been observed in patients treated with Keflex (cephalexin) , the following adverse reactions and altered laboratory tests have been reported for cephalosporin class antibiotics:
Adverse Reactions - Fever, colitis, aplastic anemia, hemorrhage, renal dysfunction, and toxic nephropathy. Several cephalosporins have been implicated in triggering seizures, particularly in patients with renal impairment when the dosage was not reduced (see INDICATIONS AND USAGE and PRECAUTIONS, General). If seizures associated with drug therapy should occur, the drug should be discontinued. Anticonvulsant therapy can be given if clinically indicated.
Altered Laboratory Tests - Prolonged prothrombin time, increased BUN, increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated LDH, pancytopenia, leukopenia, and agranulocytosis.
Read the entire FDA prescribing information for Keflex (Cephalexin) »
Additional Keflex Information
Keflex - User Reviews
Keflex User Reviews
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Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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