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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 of Keflex include: diarrhea, dizziness, tiredness, headache, stomach upset, abdominal pain, joint pain, vaginal itching or discharge, 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
The following serious events are described in greater detail in the Warning and Precautions section:
- Hypersensitivity reactions [see WARNINGS AND PRECAUTIONS]
- Clostridium difficile-associated diarrhea [see WARNINGS AND PRECAUTIONS]
- Direct Coombs' Test Seroconversion [see WARNINGS AND PRECAUTIONS]
- Seizure Potential [see WARNINGS AND PRECAUTIONS]
- Effect on Prothrombin Activity [see WARNINGS AND PRECAUTIONS]
- Development of Drug-Resistant Bacteria [see WARNINGS AND PRECAUTIONS]
Clinical Trials Experience
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice
In clinical trials, the most frequent adverse reaction was diarrhea. Nausea and vomiting, dyspepsia, gastritis, and abdominal pain have also occurred. As with penicillins and other cephalosporins, transient hepatitis and cholestatic jaundice have been reported.
Other reactions have included hypersensitivity reactions, genital and anal pruritus, genital candidiasis, vaginitis and vaginal discharge, dizziness, fatigue, headache, agitation, confusion, hallucinations, arthralgia, arthritis, and joint disorder. Reversible interstitial nephritis has been reported. Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia, and slight elevations in aspartate transaminase (AST) and alanine transaminase (ALT) have been reported.
In addition to the adverse reactions listed above that have been observed in patients treated with KEFLEX, the following adverse reactions and other altered laboratory tests have been reported for cephalosporin class antibacterial drugs:
Other Adverse Reactions
Altered Laboratory Tests
Prolonged prothrombin time, increased blood urea nitrogen (BUN), increased creatinine, elevated alkaline phosphatase, elevated bilirubin, elevated lactate dehydrogenase (LDH), pancytopenia, leukopenia, and agranulocytosis.
Read the entire FDA prescribing information for Keflex (Cephalexin)
Additional Keflex Information
Keflex - User Reviews
Keflex User Reviews
Now you can gain knowledge and insight about a drug treatment with Patient Discussions.
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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