Keflex Side Effects
Generic name: cephalexin
Note: This document contains side effect information about cephalexin. Some of the dosage forms listed on this page may not apply to the brand name Keflex.
Some side effects of Keflex may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
For the Consumer
Applies to cephalexin: oral capsule, oral powder for suspension, oral tablet, oral tablet for suspension
Along with its needed effects, cephalexin (the active ingredient contained in Keflex) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking cephalexin:More common
- Abdominal or stomach pain
- blistering, peeling, or loosening of the skin
- clay-colored stools
- dark urine
- general tiredness and weakness
- joint or muscle pain
- light-colored stools
- loss of appetite
- nausea and vomiting
- red skin lesions, often with a purple center
- red, irritated eyes
- sore throat
- sores, ulcers, or white spots in the mouth or on the lips
- unpleasant breath odor
- unusual tiredness or weakness
- upper right abdominal or stomach pain
- vomiting of blood
- yellow eyes or skin
- Abdominal or stomach cramps or tenderness
- back or leg pains
- black, tarry stools
- bleeding gums
- blood in the urine or stools
- chest pain
- coughing up blood
- diarrhea, watery and severe, which may also be bloody
- difficulty with breathing or swallowing
- fast heartbeat
- general body swelling
- increased menstrual flow or vaginal bleeding
- increased thirst
- large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
- loss of appetite
- painful or difficult urination
- pale skin
- pinpoint red spots on the skin
- prolonged bleeding from cuts
- puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
- red or black, tarry stools
- red or dark brown urine
- shortness of breath
- swollen or painful glands
- tightness in the chest
- unusual bleeding or bruising
- unusual weight loss
- watery or bloody diarrhea
Some side effects of cephalexin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:Incidence not known
- Acid or sour stomach
- burning feeling in the chest or stomach
- difficulty with moving
- dry mouth
- hives or welts
- irregular heartbeats
- itching of the vagina or genital area
- muscle pain or stiffness
- pain during sexual intercourse
- pain, swelling, or redness in the joints
- redness of the skin
- seeing, hearing, or feeling things that are not there
- stomach upset
- trouble with sleeping
- white or brownish vaginal discharge
For Healthcare Professionals
Applies to cephalexin: oral capsule, oral powder for reconstitution, oral tablet, oral tablet dispersible
Cephalexin is generally well-tolerated. Large studies report an overall 6% incidence of side effects, some of which may not be related to cephalexin (the active ingredient contained in Keflex)
Up to 20% of patients with a penicillin allergy may be allergic to cephalexin (the active ingredient contained in Keflex)
Hypersensitivity side effects have included fever, urticaria, rash, eosinophilia, anaphylaxis, angioedema, contact dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, acute paronychia, and hepatitis.
Gastrointestinal side effects have included diarrhea, nausea, vomiting, dyspepsia, abdominal cramping, anorexia, and anal pruritus. Diarrhea due to Clostridium difficile colitis has been reported with some cephalosporins.
If diarrhea occurs and it does not resolve with discontinuation of the drug and/or institution of standard antidiarrheal therapy, pseudomembranous colitis should be suspected.
Hepatic side effects have included transient elevations of liver function tests, transient hepatitis, and rare cases of cholestatic jaundice.
Renal side effects have rarely included interstitial nephritis. Reversible fever, azotemia, pyuria and eosinophiluria are the hallmarks of cephalosporin-induced interstitial nephritis. Acute tubular necrosis has also been reported.
Hematologic side effects have included eosinophilia, neutropenia, thrombocytopenia and hemolytic anemia.
Nervous system side effects have included dizziness, fatigue, headache, agitation, confusion, and hallucinations. Reversible ototoxicity and vertigo, apparently due to labyrinthine disease, have been reported in a few patients with renal disease.
Genitourinary side effects have included genital pruritus, genital moniliasis, vaginitis, and vaginal discharge.
Musculoskeletal side effects have included arthralgia, arthritis, and joint disorder.
Dermatologic side effects have included urticaria, rash, contact dermatitis, erythema multiforme, and toxic epidermal necrolysis. Acute generalized exanthematous pustulosis has been reported.
More Keflex resources
- Keflex Consumer Overview
- Keflex Prescribing Information (FDA)
- Keflex Advanced Consumer (Micromedex) - Includes Dosage Information
- Keflex Monograph (AHFS DI)
- 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)
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