|Systematic (IUPAC) name|
(7R)-3-Methyl-7- (α- D -phenylglycylamino) -3-cephem-4-carboxylic acid monohydrate
|Trade names||Keflex, Cepol, Ceporex, others|
|Licence data||US FDA:|
|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|
|ATC code||J01 QJ51|
|Molar mass||347.39 g/mol|
|Melting point||326.8 °C (620.2 °F)|
Cefalexin, also spelled cephalexin, is an antibiotic that can treat a number of bacterial infections. It kills gram-positive and some gram-negative bacteria by disrupting the growth of the bacterial cell wall. Cefalexin is a beta-lactam antibiotic within the class of first-generation cephalosporins. It works similarly to other agents within this class, including intravenous cefazolin, but can be taken by mouth.
Cefalexin can treat certain bacterial infections, including those of the middle ear, bone and joint, skin, and urinary tract. It may also be used for certain types of pneumonia, strep throat, and to prevent bacterial endocarditis. Cefalexin is not effective against infections caused by methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus, or Pseudomonas. Like other antibiotics, cefalexin cannot treat viral infections, such as the flu, common cold or acute bronchitis. Cefalexin can be used in those who have mild or moderate allergies to penicillin. However, it is not recommended in those with severe penicillin allergies.
Common side effects include upset stomach and diarrhea. An allergic reaction and infection with Clostridium difficile, a type of diarrhea, is also possible. To date, no evidence of harm to the baby has been found when used during pregnancy or breast feeding. It can be used in children and those over 65 years of age. Those with kidney problems may require a decrease in dose.
In 2012, cefalexin was one of the top 100 most prescribed medications in the United States. In Canada, it was the 5th most common antibiotic used in 2013. In Australia, it is one of the top 15 most prescribed medications. Cefalexin was developed in 1967 and first marketed in 1969 and 1970 by a number of companies, including Glaxo Wellcome and Eli Lilly and Company under the names Keflex and Ceporex, among others. Generic drug versions are available under several other trade names and are inexpensive. Cefalexin is on the World Health Organization's List of Essential Medicines, the most important medications needed in a health system.
Cefalexin can treat a number of bacterial infections including: otitis media, streptococcal pharyngitis, bone and joint infections, pneumonia, cellulitis, and urinary tract infections. It may be used to prevent bacterial endocarditis. It can also be used for the prevention of recurrent urinary-tract infections.
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. 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.
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. Use during breast feeding is generally safe.
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. Hypersensitivity reactions include skin rashes, urticaria, fever, and anaphylaxis. Pseudomembranous colitis and Clostridium difficile has been reported with use of cefalexin.
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.
Like other β-lactam antibiotics, renal excretion of cefalexin is delayed by probenecid. Alcohol consumption does not have a negative interaction with cefalexin, but reduces the rate at which it is absorbed. Cefalexin also interacts with metformin, an antidiabetic drug, and this can lead to higher concentrations of metformin in the body.
Mechanism of action
Cefalexin is a beta-lactam antibiotic of the cephalosporin family. It is bactericidal and acts by inhibiting synthesis of the peptidoglycan layer of the bacterial cell wall. 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. It is most active against gram-positive cocci, and has moderate activity against some gram-negative bacilli. 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.
Society and culture
Cefalexin is on the World Health Organization's List of Essential Medicines, the most important medications needed in a health system. The World Health Organization classifies cephalexin as a highly important antimicrobial in their list of Critically Important Antimicrobials for Human Medicine.
Common brand names for cefalexin include Keflex, Cepol, Ceporexine, Ceporex, Cefadal, Derantel, Mecilex, Medoxine, Sporibest (Bionova), Xahl, and Tokiolexin.
- McPherson, Edwin M. (2007). Pharmaceutical Manufacturing Encyclopedia. (3rd ed.). Burlington: Elsevier. p. 915. ISBN 9780815518563.
- 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
- "Cephalexin". The American Society of Health-System Pharmacists. Retrieved Apr 21, 2014.
- 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. ISBN 978-0071624428.
- "Prescribing medicines in pregnancy database". Australian Government. 3 March 2014. Retrieved 22 April 2014.
- Wendy Jones (2013). Breastfeeding and Medication. Routledge. p. 227. ISBN 9781136178153.
- Bartholow, Michael. "Top 200 Drugs of 2012". Pharmacy Times. Retrieved 22 April 2014.
- "Human Antimicrobial Drug Use Report 2012/2013" (PDF). Public Health Agency of Canada (PHAC). November 2014. Retrieved February 24, 2015.
- 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. ISBN 9781742493053.
- Hey, Edmund, ed. (2007). Neonatal formulary 5 drug use in pregnancy and the first year of life (5th ed.). Blackwell. p. 67. ISBN 9780470750353.
- Ravina, Enrique (2011). The evolution of drug discovery : from traditional medicines to modern drugs (1. Aufl. ed.). Weinheim: Wiley-VCH. p. 267. ISBN 9783527326693.
- Hanlon, Geoffrey; Hodges, Norman (2012). Essential Microbiology for Pharmacy and Pharmaceutical Science. Hoboken: Wiley. p. 140. ISBN 9781118432433.
- "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. p. 6. Retrieved 22 April 2014.
- "Lexicomp: Cefalexin".
- "Lexicomp: Antibacterials".
- "FDA Cephalexin drug label" (PDF). Retrieved 18 April 2014.
- "Cephalexin Side Effects". Drugs.com. Retrieved 9 February 2015.
- "Cefalexin". Lexicomp. Retrieved 18 April 2014.
- Haberfeld, H, ed. (2009). Austria-Codex (in German) (2009/2010 ed.). Vienna: Österreichischer Apothekerverlag. ISBN 3-85200-196-X.
- "Cefalexin". Lexicomp. Retrieved 17 April 2014.
- "Cefalexin (Cefalexin 250mg capsules)". NHS Choices.
- 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. doi:10.1002/jps.2600800602. PMID 1941538.
- 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. doi:10.1515/dmdi.2002.19.1.41. PMID 12222753.
- Bothara SS, Kadam KR, Mahadik KG (2006). "Antibiotics". Principles of Medicinal Chemistry 1 (14th ed.). Pune: Nirali Prakashan. p. 81. ISBN 8185790043.
- Fisher JF, Meroueh SO, Mobashery S (Feb 2005). "Bacterial resistance to beta-lactam antibiotics: compelling opportunism, compelling opportunity". Chemical Reviews 105 (2): 395–424. doi:10.1021/cr030102i. PMID 15700950.
- "Cefalexin". Lexicomp. Retrieved 17 April 2014.
- Drawz SM, Bonomo RA (Jan 2010). "Three decades of beta-lactamase inhibitors". Clinical Microbiology Reviews 23 (1): 160–201. doi:10.1128/CMR.00037-09. PMC 2806661. PMID 20065329.
- "Critically Important Medicines for Human Medicine, 3rd Revision 2011" (PDF). World Health Organization. Retrieved 24 February 2015.