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Cefalexin: Wikis


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Systematic (IUPAC) name
(6R,7R)-7-{[(2R)-2-amino-2-phenylacetyl]amino}- 3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene- 2-carboxylic acid
CAS number 15686-71-2
ATC code J01DB01 QJ51DA01
PubChem 2666
DrugBank APRD00250
ChemSpider 25541
Chemical data
Formula C16H17N3O4S 
Mol. mass 347.39 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability Well absorbed
Metabolism 90% excreted unchanged
Half life 0.9 hours
Excretion Renal
Therapeutic considerations
Pregnancy cat. A(AU) B(US)
Legal status Prescription Only (S4) (AU) POM (UK)
Routes Oral
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Cefalexin (INN) (pronounced /ˌsɛfəˈlɛksɨn/) or cephalexin (USAN) is a first-generation cephalosporin antibiotic, introduced in 1967 by Eli Lilly and Company.[1] 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), Sporidex (Ranbaxy) or Nufex.

As of 2008, cefalexin was the most popular cephalosporin antibiotic in the United States, with more than 25 million prescriptions of its generic versions alone, for US$255 million in sales.[2][3]


Clinical use


Cephalexin is used to treat urinary tract infections, respiratory tract infections, and skin and soft tissue infections. It is also sometimes used to treat acne.

In addition to being a rational first-line treatment for cellulitis, it is a useful alternative to penicillins in patients with penicillin hypersensitivity.


Side effects from Cephalexin include - but are not limited to - diarrhea; dizziness; headache; indigestion; joint pain; stomach pain; tiredness. The drug can also cause yellowing of the eyes or skin; red, blistered, swollen or peeling skin; unusual bruising or bleeding; decreased urination; severe cramps; confusion. An allergic reaction to this medicine is unlikely, but seek immediate medical attention if it occurs. Symptoms of an allergic reaction include rash, itching, swelling, or trouble breathing.


Cefalexin is commonly marketed in the following forms:

Pulvules 250 mg
Pulvules 500 mg
Oral Suspension 125 mg per 5 mL (1 teaspoon)
Oral Suspension 250 mg per 5 mL (1 teaspoon)
Tablet 500 mg

(Note: a pulvule is a capsule that becomes slick when moistened by saliva thus making it easier to swallow.)

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

A version of Keflex 750 mg capsules is marketed for twice-daily dosage, to improve patients' compliance. However, it is not a sustained release formulation, and since it is more expensive than the older strengths, some physicians prescribe three 250 mg capsules to be taken twice daily, as a cheaper alternative.[citation needed]

In Finland, Cephalexin is marketed under several names. Orion, a Finnish pharmaceutical company, markets Kefexin as 250, 500 and 750 mg tablets (PDF in Finnish)[4]. The recommended dosage for adults and children (six years and older, weighing over 30 kg) is 1 to 4 grams per day, with patients with renal dysfunction requiring longer periods between doses[5].


  1. ^ Sneader, Walter (2005). "Cephalosporin analogues". Drug discovery: a history. New York: Wiley. pp. 324. ISBN 0-471-89980-1. Retrieved 2009-06-26. 
  2. ^ "2008 Top 200 generic drugs by total prescriptions" PDF (332.8 KB). Drug Topics (May 26, 2009). Retrieved on July 24, 2009.
  3. ^ "2008 Top 200 generic drugs by retail dollars" PDF (399.4 KB). Drug Topics (May 26, 2009). Retrieved on July 24, 2009.
  4. ^
  5. ^

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