Cephalexin (Keflex): Uses, Warnings, and Key Facts
Quick summary Cephalexin is an oral cephalosporin antibiotic used for certain bacterial infections, including some respiratory tract, skin, urinary tract, ear, and dental infections. The exact use, dose, and duration depend on the infection...
This content is for educational purposes only and does not replace medical advice, diagnosis or treatment from a qualified healthcare professional.
Quick summary
Cephalexin is an oral cephalosporin antibiotic used for certain bacterial infections, including some respiratory tract, skin, urinary tract, ear, and dental infections. The exact use, dose, and duration depend on the infection and the official product information.
Medical disclaimer
This article is for general information only and does not replace advice from a doctor, pharmacist, or the official medicine leaflet. Do not use it to diagnose an infection or to decide on treatment changes.
What is cephalexin?
Cephalexin, also written as cefalexin, is a semi-synthetic antibiotic in the cephalosporin family. It is taken by mouth and is used against infections caused by susceptible microorganisms.
Brand names mentioned in the source include Keflex, Zartan, Keftab, and Daxbia.
How cephalexin works
Cephalexin works by inhibiting bacterial cell wall synthesis. This bactericidal action helps stop bacteria from growing and surviving.
What cephalexin is used for
The source lists cephalexin for treatment of infections due to sensitive microorganisms, including:
- Respiratory tract infections
- Otitis media
- Skin and subcutaneous tissue infections
- Urinary tract infections, including acute prostatitis
- Dental infections
The exact indication should always be confirmed in the official product information for the specific medicine being used.
Dosage information from the source
Important: This section summarizes the original content and is not a prescription. A clinician should determine the correct dose for each person.
| Group | Source summary |
|---|---|
| Adults | 1–4 g/day in divided doses, usually 250 mg every 6 hours; maximum 4 g/day. |
| Children | 25–50 mg/kg/day in divided doses every 6 hours; double doses in severe infection. |
| Otitis media with undetermined causal germ | 75–100 mg/kg/day in 2–4 doses to cover H. influenzae infection. |
The source also notes continuing treatment for at least 48–72 hours after symptoms disappear, and at least 10 days for beta-hemolytic streptococcal infection.
Contraindications
The source lists hypersensitivity to cephalosporins as a contraindication.
Warnings and precautions
Allergy history
Use extreme caution if cephalexin is needed in people with a history of penicillin allergy or other drug allergies.
Diarrhea and colitis
The source warns about the risk of pseudomembranous colitis. Diarrhea during antibiotic treatment should be taken seriously and reviewed by a healthcare professional.
Superinfection
Prolonged treatment may allow non-sensitive microorganisms to grow, so monitoring may be needed.
Kidney impairment
In kidney failure, the source advises caution, monitoring, and dose reduction.
Skin reactions
Cases of acute generalized exanthematous pustulosis have been reported. The source advises close monitoring for skin reactions and stopping treatment if they occur, with consideration of an alternative therapy.
Drug and test interactions
- Probenecid: may inhibit renal excretion of cephalexin.
- Metformin: the source notes increased plasma concentration.
- Laboratory tests: false-positive results may occur in the Coombs test and in urine glucose testing with Benedict or Fehling solutions or copper sulfate tablets.
Pregnancy and breastfeeding
Pregnancy: The source says risk-benefit should be assessed. Animal studies did not show harmful effects, but there are no adequate controlled studies in pregnant women.
Breastfeeding: Cephalexin is excreted in human milk. The source advises caution in lactating women.
Driving and machinery
The source states there is no evidence that cephalexin affects the ability to drive or use machinery.
Possible adverse reactions
The source lists the following adverse reactions, including some rare and serious ones:
- Nausea, vomiting, diarrhea, dyspepsia, abdominal pain, fatigue
- Transient hepatitis, jaundice, altered liver function tests
- Anaphylaxis, allergic reactions, urticaria, angioneurotic edema
- Eosinophilia, neutropenia, thrombocytopenia, hemolytic anemia
- Dizziness, headache, hallucinations
- Skin rash, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis
- Interstitial nephritis, pseudomembranous colitis
- Genital and anal itching, vaginitis, vaginal moniliasis
If a serious reaction is suspected, urgent medical assessment is needed.
FAQ about cephalexin
▸ What infections is cephalexin used for?
The source lists respiratory tract, skin and subcutaneous tissue, urinary tract, otitis media, and dental infections caused by sensitive microorganisms.
▸ Is cephalexin an antibiotic?
Yes. It is a cephalosporin antibiotic taken by mouth.
▸ Can cephalexin cause diarrhea?
Yes. Diarrhea is listed among the adverse reactions, and the source also warns about pseudomembranous colitis.
▸ Is cephalexin safe in pregnancy?
The source recommends assessing risk and benefit. It notes no harmful effects in animal studies, but adequate controlled studies in pregnant women are lacking.
▸ Does cephalexin interact with other medicines?
The source mentions probenecid, metformin, and some laboratory test interferences. A pharmacist can help check the full medicine list.
Safety reminder
Before using cephalexin, verify the exact product, indication, dose, and duration in the official leaflet or with a healthcare professional. Seek prompt medical advice for rash, breathing problems, severe diarrhea, or other concerning symptoms.
Sources and reference links
The original content cites FDA and U.S. National Library of Medicine resources for ingredient identification and product information. For official medicine details, consult the FDA medication guide and the product-specific leaflet.
Medical disclaimer
This content is for educational purposes only. It should not be used as a substitute for professional medical advice, diagnosis or treatment. Always ask a doctor, pharmacist or qualified healthcare professional before starting, stopping or changing any medicine.
Sources and verification
The following sources or official references are listed to support verification of the medicine information discussed in this article.
Medicine information can change and may vary depending on country, product formulation, patient history and professional guidance. Always check official medicine information and ask a healthcare professional for personal medical questions.