Systematic (IUPAC) name
(7R)-3-Methyl-7- (α- D -phenylglycylamino) -3-cephem-4-carboxylic acid monohydrate
Clinical data
Trade names Keflex, Cepol, Ceporex, others[1]
Licence data US FDA:
  • AU: A
  • US: B (No risk in non-human studies)
Legal status
Routes of
Pharmacokinetic data
Bioavailability Well absorbed
Protein binding 15%
Metabolism 80% excreted unchanged in urine within 6 hours of administration
Biological half-life For an adult with normal renal function, the serum half-life is 0.5–1.2 hours[2]
Excretion Renal
CAS Registry Number  Y
ATC code J01 QJ51
PubChem CID:
DrugBank  Y
ChemSpider  Y
Chemical data
Formula C16H17N3O4S
Molecular mass 347.39 g/mol
Physical data
Melting point 326.8 °C (620.2 °F)

Cefalexin, also spelled cephalexin, is an health system.[13]


  • Medical uses 1
    • Pregnancy and breastfeeding 1.1
  • Adverse effects 2
  • Interactions 3
  • Mechanism of action 4
  • Society and culture 5
    • Names 5.1
  • References 6
  • External links 7

Medical uses

A course of cefalexin capsules, commonly prescribed for infections

Cefalexin can treat a number of bacterial infections including: otitis media, streptococcal pharyngitis, bone and joint infections, pneumonia, cellulitis, and urinary tract infections.[3] It may be used to prevent bacterial endocarditis.[3] It can also be used for the prevention of recurrent urinary-tract infections.[14]

Cefalexin does not treat methicillin-resistant Staphylococcus aureus infections.[14]

Cefalexin is a useful alternative to penicillins in patients with penicillin intolerance. For example, penicillin is the treatment of choice for respiratory tract infections caused by Streptococcus, but cefalexin may be used as an alternative in penicillin-intolerant patients.[15] Caution must be exercised when administering cephalosporin antibiotics to penicillin-sensitive patients, because cross sensitivity with beta-lactam antibiotics has been documented in up to 10% of patients with a documented penicillin allergy.[16]

Pregnancy and breastfeeding

It is pregnancy category B in the United States and category A in Australia, meaning that no evidence of harm has been found after being taken by many pregnant women.[3][5] Use during breast feeding is generally safe.[6]

Adverse effects

The most common adverse effects of cefalexin, like other oral cephalosporins, are gastrointestinal (stomach area) disturbances and hypersensitivity reactions. Gastrointestinal disturbances include nausea, vomiting, and diarrhea, diarrhea being most common.[17] Hypersensitivity reactions include skin rashes, urticaria, fever, and anaphylaxis.[18] Pseudomembranous colitis and Clostridium difficile has been reported with use of cefalexin.[18]

Signs and symptoms of an allergic reaction include rash, itching, swelling, trouble breathing, or red, blistered, swollen, or peeling skin. Overall, cefalexin allergy occurs in less than 0.1% of patients, but it is seen in 1% to 10% of patients with a penicillin allergy.[19]


Like other β-lactam antibiotics, renal excretion of cefalexin is delayed by probenecid.[20] Alcohol consumption does not have a negative interaction with cefalexin,[21] but reduces the rate at which it is absorbed.[22] Cefalexin also interacts with metformin, an antidiabetic drug,[18] and this can lead to higher concentrations of metformin in the body.[18][23]

Mechanism of action

Cefalexin is a beta-lactam antibiotic of the cephalosporin family.[24] It is bactericidal and acts by inhibiting synthesis of the peptidoglycan layer of the bacterial cell wall.[25] As cefalexin closely resembles d-alanyl-d-alanine, an amino acid ending on the peptidoglycan layer of the cell wall, it is able to irreversibly bind to the active site of PBP, which is essential for the synthesis of the cell wall.[25] It is most active against gram-positive cocci, and has moderate activity against some gram-negative bacilli.[26] However, some bacterial cells have the enzyme β-lactamase, which hydrolyzes the beta-lactam ring, rendering the drug inactive. This contributes to antibacterial resistance towards cephalexin.[27]

Society and culture

Cefalexin is on the

  • U.S. National Library of Medicine: Drug Information Portal — Cephalexin

External links

  1. ^ a b McPherson, Edwin M. (2007). Pharmaceutical Manufacturing Encyclopedia. (3rd ed.). Burlington: Elsevier. p. 915.  
  2. ^ 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
  3. ^ a b c d e f g h i j "Cephalexin". The American Society of Health-System Pharmacists. Retrieved Apr 21, 2014. 
  4. ^ Brunton, Laurence L. (2011). "53, Penicillins, Cephalosporins, and Other β-Lactam Antibiotics". Goodman & Gilman's pharmacological basis of therapeutics. (12th ed.). New York: McGraw-Hill.  
  5. ^ a b "Prescribing medicines in pregnancy database". Australian Government. 3 March 2014. Retrieved 22 April 2014. 
  6. ^ a b Wendy Jones (2013). Breastfeeding and Medication. Routledge. p. 227.  
  7. ^ Bartholow, Michael. "Top 200 Drugs of 2012". Pharmacy Times. Retrieved 22 April 2014. 
  8. ^ "Human Antimicrobial Drug Use Report 2012/2013" (PDF). Public Health Agency of Canada (PHAC). November 2014. Retrieved February 24, 2015. 
  9. ^ Australia's Health 2012: The Thirteenth Biennial Health Report of the Australian Institute of Health and Welfare. Australian Institute of Health and Welfare. 2012. p. 408.  
  10. ^ Hey, Edmund, ed. (2007). Neonatal formulary 5 drug use in pregnancy and the first year of life (5th ed.). Blackwell. p. 67.  
  11. ^ Ravina, Enrique (2011). The evolution of drug discovery : from traditional medicines to modern drugs (1. Aufl. ed.). Weinheim: Wiley-VCH. p. 267.  
  12. ^ Hanlon, Geoffrey; Hodges, Norman (2012). Essential Microbiology for Pharmacy and Pharmaceutical Science. Hoboken: Wiley. p. 140.  
  13. ^ a b "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. p. 6. Retrieved 22 April 2014. 
  14. ^ a b "Lexicomp: Cefalexin". 
  15. ^ "Lexicomp: Antibacterials". 
  16. ^ "FDA Cephalexin drug label" (PDF). Retrieved 18 April 2014. 
  17. ^ "Cephalexin Side Effects". Drugs.com. Retrieved 9 February 2015. 
  18. ^ a b c d "Cefalexin". Lexicomp. Retrieved 18 April 2014. 
  19. ^ Haberfeld, H, ed. (2009). Austria-Codex (in German) (2009/2010 ed.). Vienna: Österreichischer Apothekerverlag.  
  20. ^ "Cefalexin". Lexicomp. Retrieved 17 April 2014. 
  21. ^ "Cefalexin (Cefalexin 250mg capsules)". NHS Choices. 
  22. ^ Barrio Lera JP, Alvarez AI, Prieto JG (Jun 1991). "Effects of ethanol on the pharmacokinetics of cephalexin and cefadroxil in the rat". Journal of Pharmaceutical Sciences 80 (6): 511–6.  
  23. ^ Jayasagar G, Krishna Kumar M, Chandrasekhar K, Madhusudan Rao C, Madhusudan Rao Y (2002). "Effect of cephalexin on the pharmacokinetics of metformin in healthy human volunteers". Drug Metabolism and Drug Interactions 19 (1): 41–8.  
  24. ^ Bothara SS, Kadam KR, Mahadik KG (2006). "Antibiotics". Principles of Medicinal Chemistry 1 (14th ed.). Pune: Nirali Prakashan. p. 81.  
  25. ^ a b Fisher JF, Meroueh SO, Mobashery S (Feb 2005). "Bacterial resistance to beta-lactam antibiotics: compelling opportunism, compelling opportunity". Chemical Reviews 105 (2): 395–424.  
  26. ^ "Cefalexin". Lexicomp. Retrieved 17 April 2014. 
  27. ^ Drawz SM, Bonomo RA (Jan 2010). "Three decades of beta-lactamase inhibitors". Clinical Microbiology Reviews 23 (1): 160–201.  
  28. ^ "Critically Important Medicines for Human Medicine, 3rd Revision 2011" (PDF). World Health Organization. Retrieved 24 February 2015. 
  29. ^ https://scifinder.cas.org


Common brand names for cefalexin include Keflex, Cepol, Ceporexine, Ceporex, Cefadal, Derantel, Mecilex, Medoxine, Sporibest (Bionova), Xahl, and Tokiolexin.[29]

Cefalexin is the INN and BAN while cephalexin is the USAN and AAN.