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Cefalexin

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Cefalexin
Clinical data
Pregnancy
category
  • AU: A
Routes of
administration		Oral
ATC code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • UK: POM (Prescription only)
Pharmacokinetic data
BioavailabilityWell absorbed
Protein binding15%
Metabolism80% excreted unchanged in urine within 6 hours of administration
Elimination half-lifeFor an adult with normal renal function, the serum half-life is 0.5-1.2 hours[1]
ExcretionRenal
Identifiers
  • (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
PubChem CID
DrugBank
ChemSpider
UNII
KEGG
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.036.142 Edit this at Wikidata
Chemical and physical data
FormulaC16H17N3O4S
Molar mass347.39 g/mol g·mol−1
3D model (JSmol)
  • O=C2N1/C(=C(\CS[C@@H]1[C@@H]2NC(=O)[C@@H](c3ccccc3)N)C)C(=O)O
  • InChI=1S/C16H17N3O4S/c1-8-7-24-15-11(14(21)19(15)12(8)16(22)23)18-13(20)10(17)9-5-3-2-4-6-9/h2-6,10-11,15H,7,17H2,1H3,(H,18,20)(H,22,23)/t10-,11-,15-/m1/s1 checkY
  • Key:ZAIPMKNFIOOWCQ-UEKVPHQBSA-N checkY
  (verify)

Cefalexin (INN) or more commonly cephalexin (Template:PronEng) is a first-generation cephalosporin antibiotic introduced in 1967 by Eli Lilly and Company.[2][3] It is an orally administered agent with a similar antimicrobial spectrum to the intravenous agents cefalotin and cefazolin. It was first marketed as Keflex (Lilly), and is now sold under several other trade names as well.[2]

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.[4][5]

Clinical use

Main article: Cephalosporin

Cefalexin 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. In patients with mild or questionable history of penicillin allergy, cephalasporins are now thought to be relatively safe.[6] Caution should always be taken when prescribing cephalosporins to those with strong history of true penicillin hypersensitivity, however, because cefalexin and other first-generation cephalosporins are known to have a modest cross-allergy in patients with penicillin hypersensitivity.

Formulations

Cefalexin is commonly marketed in the following forms:

Formulation Dosage
Pulvules[7] (Capsules) 250 mg
Pulvules[7] 500 mg
Oral suspension 125 mg per 5 mL (1 teaspoon)
Oral suspension 250 mg per 5 mL (1 teaspoon)
Tablet 250 mg
Tablet 500 mg

Cefalexin is marketed by generic pharmaceutical manufacturers under a wide range of brand names, including: Apo-Cephalex, Biocef, Cefanox, Ceforal, Cephabos, Cephalexin, Cephorum, Ceporex, Cilex, Ialex, Ibilex, Kefexin, Keflet, Keflex, Rekosporin, 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, cefalexin is marketed under several names. Orion markets Kefexin as 250, 500 and 750 mg tablets.[8] 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.[9]

Side effects

Side effects from cefalexin include diarrhea (usually mild), dizziness, headache, indigestion, joint pain, stomach pain (usually mild) and 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 and confusion. An allergic reaction to this medicine is unlikely. Seek immediate medical attention if it occurs. Symptoms of an allergic reaction include rash, itching, swelling, or trouble breathing. Like other antibiotics, cefalexin can affect the efficacy of birth control pills; barrier contraception usage is advisable.[10]

References

  1. ^ McEvoy, G.K. (ed.). American Hospital Formulary Service - Drug Information 95. Bethesda, MD: American Society of Hospital Pharmacists, Inc., 1995 (Plus Supplements 1995)., p. 166
  2. ^ a b Sweetman, Sean C., ed. (2009). "Antibacterials". Martindale: The complete drug reference (36th ed.). London: Pharmaceutical Press. pp. 218–9. ISBN 978-0-85369-840-1.
  3. ^ Sneader, Walter (2005). "Cephalosporin analogues". Drug discovery: a history. New York: Wiley. p. 324. ISBN 0-471-89980-1. {{cite book}}: |access-date= requires |url= (help); External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)
  4. ^ Template:PDFlink. Drug Topics (May 26, 2009). Retrieved on July 24, 2009.
  5. ^ Template:PDFlink. Drug Topics (May 26, 2009). Retrieved on July 24, 2009.
  6. ^ Pichichero ME (2007). "Use of selected cephalosporins in penicillin-allergic patients: a paradigm shift". Diagnostic Microbiology and Infectious Disease. 57 (3 Suppl): 13S–18S. doi:10.1016/j.diagmicrobio.2006.12.004. PMID 17349459. {{cite journal}}: Unknown parameter |month= ignored (help)
  7. ^ a b Note: a pulvule is a trademarked name for a [gelatin]-based capsule that becomes slick when moistened by saliva, making it easier to swallow.
  8. ^ http://spc.nam.fi/indox/nam/html/nam/humpil/2/244412.pdf
  9. ^ http://spc.nam.fi/indox/nam/html/nam/humspc/2/244362.shtml
  10. ^ Mayo Clinic – Birth control pill FAQ
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