Cefalexin was developed in 1967.[7][8][9] It was first marketed in 1969 and 1970 under the names Keflex and Ceporex, among others.[10][11] It is available as a generic medication.[3][12] It is on the World Health Organization's List of Essential Medicines.[13] In 2021, it was the 96th most commonly prescribed medication in the United States, with more than 7million prescriptions.[14][15] In Canada, it was the fifth most common antibiotic used in 2013.[16] In Australia, it is one of the top 15 most prescribed medications.[17]
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.[3] Caution must be exercised when administering cephalosporin antibiotics to penicillin-sensitive patients, because cross-sensitivity with β-lactam antibiotics has been documented in up to 10% of patients with a documented penicillin allergy.[18]
It is categorized in 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]
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, the latter being the most common.[19]Hypersensitivity reactions include skin rashes, urticaria, fever, and anaphylaxis.[3]Pseudomembranous colitis and Clostridium difficile have been reported with use of cefalexin.[3] Less common and more serious side effects include bruising of the skin and yellowing of the skin or eye whites.[20]
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[citation needed]. Evidence suggests that it is seen in 1% to 10% of patients with a penicillin allergy.[21]
Cefalexin is a β-lactam antibiotic of the cephalosporin family.[26] It is bactericidal and acts by inhibiting synthesis of the peptidoglycan layer of the bacterial cell wall.[27] 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.[27] It is most active against gram-positive cocci, and has moderate activity against some gram-negative bacilli.[3] However, some bacterial cells have the enzyme β-lactamase, which hydrolyzes the β-lactam ring, rendering the drug inactive. This contributes to antibacterial resistance towards cefalexin.[28]
Cefalexin is rapidly and almost completely absorbed from the gastrointestinal tract with oral administration.[29] Absorption is slightly reduced when it is taken with food and the medication can be taken without regard for meals.[29] Peak levels of cefalexin occur about 1 hour after administration.[29] Maximal levels of cefalexin increase approximately linearly over a dose range of 250 to 1,000 mg.[29]
Like most other cephalosporins, cefalexin is not metabolized or otherwise inactivated in the body.[25][30]
The elimination half-life of cefalexin is approximately 30 to 60 minutes in people with normal renal function.[30][29] Therapeutic levels of cefalexin with oral administration are maintained for 6 to 8 hours.[29] For this reason, cefalexin is typically administered once every 6 to 12 hours depending on the indication.[29] More than 90% of cefalexin is excreted unchanged in the urine within 8 hours.[29]
According to Plumb's Veterinary Medication Guides, cefalexin can be used in treating skin, respiratory tract, and urinary tract infections. Specifically, it can be used to treat pyoderma in dogs.[35] The U.S. Food and Drug Administration (FDA) has approved it for use in humans and dogs but not for other species. Like other drugs approved for human use, cefalexin may be prescribed by veterinarians for animals in certain situations.[36]
Cefalexin (Lexylan) is indicated for the treatment of cattle, dogs, and cats in the European Union.[37]
^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
^US patent 3275626, Morin RB, Jackson BG, "Penicillin conversion via sulfoxide", published 1966-09-27, issued 1966-09-27, assigned to Eli Lilly and Co"Espacenet - Bibliographic data". Archived from the original on 25 September 2022. Retrieved 3 March 2020.
^US patent 3507861, Morin RB, Jackson BG, "Certain 3-methyl-cephalosporin compounds", published 1970-04-21, issued 1970-04-21, assigned to Eli Lilly and Co"Espacenet - Bibliographic data". Archived from the original on 25 September 2022. Retrieved 3 March 2020.
^McPherson EM (2007). "Cefalexin". Pharmaceutical Manufacturing Encyclopedia (3rd ed.). Burlington: Elsevier. p. 915. ISBN9780815518563. Archived from the original on 8 September 2017.
^ abWorld Health Organization (2021). World Health Organization model list of essential medicines: 22nd list (2021). Geneva: World Health Organization. hdl:10665/345533. WHO/MHP/HPS/EML/2021.02.
^"Cephalexin (Oral Route)". Mayo Clinic. Mayo Foundation for Medical Education and Research. Retrieved 14 November 2022.
^Barrio Lera JP, Alvarez AI, Prieto JG (June 1991). "Effects of ethanol on the pharmacokinetics of cephalexin and cefadroxil in the rat". Journal of Pharmaceutical Sciences. 80 (6): 511–516. doi:10.1002/jps.2600800602. PMID1941538.
^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): 41–48. doi:10.1515/dmdi.2002.19.1.41. PMID12222753. S2CID26919498.
^ abRafiei N (2 October 2017). "Cephalexin". In Grayson M (ed.). Kucers' The Use of Antibiotics: A Clinical Review of Antibacterial, Antifungal, Antiparasitic, and Antiviral Drugs (Seventh ed.). CRC Press. pp. 364–. ISBN978-1-4987-4796-7. Archived from the original on 28 August 2021. Retrieved 13 July 2018.
^Bothara SS, Kadam KR, Mahadik KG (2006). "Antibiotics". Principles of Medicinal Chemistry. Vol. 1 (14th ed.). Pune: Nirali Prakashan. p. 81. ISBN8185790043. Archived from the original on 25 September 2022. Retrieved 7 October 2020.
^ abFisher JF, Meroueh SO, Mobashery S (February 2005). "Bacterial resistance to beta-lactam antibiotics: compelling opportunism, compelling opportunity". Chemical Reviews. 105 (2): 395–424. doi:10.1021/cr030102i. PMID15700950.