CEPHALEXIN (Keflex): What used for?

What is Cephalexin?

Cephalexin (Cefalexina) is a drug used to treat infections of the respiratory tract, skin, urethra, ear, teeth, etc. The product ingredients are Cephalexin hydrochloride (hcl), Cefalexin monohydrate, Cefalexin sodium.

The brand names of Cephalexin are: Keflex, Zartan, Keftab and Daxbia.

Mechanism of action (MOA) of Cephalexin

Semi-synthetic antibiotic of the cephalosporin family for oral administration.

As demonstrated by in vitro tests, the bactericidal action of cephalosporins is due to inhibition of cell wall synthesis.

Therapeutic indications, uses and benefits 

Treatment of the following infections due to sensitive micro-organisms: respiratory tract infections, otitis media, skin and subcutaneous tissue infections, urinary tract infections (including acute prostatitis) and dental infections.

Dosage of Cephalexin

Oral dose

Adults: 1-4 g/day in fractional doses, usually 250 mg/6 h; max. 4 g/day.

Children: 25-50 mg/kg/day, in fractionated doses/6 h (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.

Administer min. 48-72 h after disappearing symptoms. ß-hemolytic streptococcal infection, min. 10 days.


Hypersensitivity to cephalosporins.

Warnings and precautions with Cephalexin

Extreme caution if it is essential to use in people allergic to penicillins; history of drug allergy.

Risk of pseudomembranous colitis (keep in mind if diarrhoea appears) and of superinfection by non-sensitive microorganisms in prolonged treatment (monitor).

Kidney failure, monitoring and dose reduction.

Cases of acute generalized exanthematic pustulosis have been reported (closely monitor patients for skin reactions and discontinue treatment if they occur and consider a therapeutic alternative).

Kidney failure

Caution, monitor and reduce dose.

Interactions with Cephalexin

  • Renal excretion inhibited by: probenecid.
  • Increases plasma oncentration of: metformin.
  • Lab: false + in Coombs test and glucose in urine if Benedict or Fehling solution methods are used or with copper sulfate tablets.

Pregnancy and Cephalexin

Assess risk/benefit. Animal studies show no harmful effects. There are no adequate controlled studies in pregnant women.


Cephalexin is excreted in human milk.

After administration of a 500 mg dose, the drug reached a maximum level of 4 mcg/ml, gradually decreasing thereafter, and having disappeared within 8 hours of administration.

It should be administered with caution to lactating women.

Effects on driving ability

There is no evidence affects the ability to drive or use machinery.

Adverse reactions and side effects of Cephalexin

Very rare: nausea, vomiting, diarrhea, dyspepsia, abdominal pain; fatigue.

Transient hepatitis, jaundice, PFH alteration; 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.


Source: The content of this active ingredient has been written taking into account the clinical and molecular information of all medicines authorised and marketed in the United States under the Unique Ingredient Identifier (UNII) by the Substance Registration System (SRS) of the Food and Drug Administration (FDA) and the United States Pharmacopeia (USP).

In order to know in detail the information authorized by the FDA for each drug, you should consult the corresponding medication guide authorized by the FDA.


PubChem CID: 62921
NCI Thesaurus: C356

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