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Systematic (IUPAC) name
8-(2-amino-2-phenyl-acetyl)amino-4-methyl-7-oxo-2-thia-6-azabicyclo [4.2.0]oct-4-ene-5-carboxylic acid
CAS number 15686-71-2
ATC code J01DB01
PubChem 2666
DrugBank APRD00250
Chemical data
Formula C16H17N3O4S 
Mol. mass 347.39 g/mol
Pharmacokinetic data
Bioavailability Well absorbed
Metabolism 90% excreted unchanged
Half life 0.9 hours
Excretion Renal
Therapeutic considerations
Pregnancy cat.


Legal status

Prescription Only (S4)(AU) POM(UK)

Routes Oral

Cefalexin (INN) (pronounced /sɛfəˈlɛksɨn/, /kɛfə-/) or cephalexin (USAN) is a first-generation cephalosporin antibiotic. It is an orally-administered agent with a similar antimicrobial spectrum to the intravenous agents cefalotin and cefazolin. It is commonly marketed under the trade name Keflex (Lilly) or Sporidex (Ranbaxy).


Clinical use

Main article: Cephalosporin


Cefalexin is used to treat urinary tract infections, respiratory tract infections (including sinusitis, otitis media, pharyngitis, tonsillitis and pneumonia, bronchitis), skin and soft tissue infections.

Although it is not generally considered first-line therapy for any indication, it is a useful alternative to penicillins in patients with penicillin hypersensitivity. There is, however, cross-reactivity in 10% of patients with hypersensitivity to penicillins and carbapenems.


Cefalexin is commonly marketed as tablets(250 mg and 500 mg), tablets, and powder for oral suspension (125 mg/5 mL and 250 mg/5 mL).

Cephalexin is being marketed as Keflex® 750 mg as "taken twice per day". The advantage of Keflex 750 is that it provides the same total daily dose most health care professionals prescribe with only two capsules per day. By making Keflex 750 convenient for patients, compliance may be improved with this new dosing option. Keflex 750 is covered by most major insurers with an average copay of between $20 and $25. Retail price is approximately $45 for a 20 capsule supply.

It is marketed by generic pharmaceutical manufacturers under a wide range of brand names, including: Apo-Cephalex, Biocef, Cefanox, Ceporex, Cephabos, Cilex, Ialex, Ibilex, Keflet, Keflex, Keforal, Keftab, Keftal, Lopilexin, Novo-Lexin, Ospexin, Zephalexin, Panixine Disperdose and Sporidex.

See also

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cefalexin". A list of authors is available in Wikipedia.
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