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| Pronunciation | /ˌsɛfəˈlɛksɪn/ |
| Trade names | Keflex, others |
| Other names | cephalexin, cephalexin (BANUK), cephalexin (USANUS) |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682733 |
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| Routes of administration | By mouth |
| Drug class | First-generation cephalosporin |
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| Pharmacokinetic data | |
| Bioavailability | Well absorbed |
| Protein binding | 15% |
| Metabolism | 80% excreted unchanged in urine within 6 hours of administration |
| Eliminationhalf-life | 0.6–1.2 hours[3] |
| Excretion | Kidney |
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| ECHA InfoCard | 100.036.142 |
| Chemical and physical data | |
| Formula | C16H17N3O4S |
| Molar mass | 347.39 g·mol−1 |
| 3D model (JSmol) | |
| Melting point | 326.8 °C (620.2 °F) |
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Cefalexin, also spelledcephalexin, is anantibiotic that can treat a number ofbacterial infections.[4] It killsgram-positive and somegram-negative bacteria by disrupting the growth of the bacterial cell wall.[4] Cefalexin is aβ-lactam antibiotic within the class of first-generationcephalosporins.[4] It works similarly to other agents within this class, including intravenouscefazolin, but can be takenby mouth.[5]
Cefalexin can treat certain bacterial infections, including those of themiddle ear,bone andjoint,skin, andurinary tract.[4] It may also be used for certain types ofpneumonia andstrep throat and to preventbacterial endocarditis.[4] Cefalexin is not effective against infections caused bymethicillin-resistantStaphylococcus aureus (MRSA), mostEnterococcus, orPseudomonas.[4] Like other antibiotics, cefalexin cannot treatviral infections, such as theflu,common cold oracute bronchitis.[4] Cefalexin can be used in those who have mild or moderate allergies topenicillin.[4] However, it is not recommended in those with severe penicillin allergies.[4]
Commonside effects includestomach upset anddiarrhea.[4]Allergic reactions or infections with Clostridioides difficile, a cause of diarrhea, are also possible.[4] Use duringpregnancy orbreastfeeding does not appear to be harmful to the fetus.[4][6][7] It can be used in children and those over 65 years of age.[4] Those withkidney problems may require a decrease in dose.[4]
Cefalexin was developed in 1967.[8][9][10] It was first marketed in 1969 under the brand nameKeflex.[11][12] It is available as ageneric medication.[4][13] It is on theWorld Health Organization's List of Essential Medicines.[14] In 2022, it was the 101st most commonly prescribed medication in the United States, with more than 6 million prescriptions.[15][16] In Canada, it was the fifth most common antibiotic used in 2013.[17] In Australia, it was one of the top 10 most prescribed medications between 2017 and 2023.[18]
Cefalexin can treat a number of bacterial infections includingotitis media,streptococcal pharyngitis, bone and joint infections,pneumonia,cellulitis, andurinary tract infections.[4] It may be used to preventbacterial endocarditis.[4] It can also be used for the prevention of recurrent urinary-tract infections.[4]
Cefalexin does not treatmethicillin-resistantStaphylococcus aureus infections.[4]
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 byStreptococcus, but cefalexin may be used as an alternative in penicillin-intolerant patients.[4] 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.[19]
It is categorized in category A in Australia meaning that no evidence of harm has been found after being taken by many pregnant women.[4][6] Use duringbreastfeeding is generally safe.[7]
The most common adverse effects of cefalexin, like other oral cephalosporins, are gastrointestinal (stomach area) disturbances and hypersensitivity reactions. Gastrointestinal disturbances includenausea,vomiting, anddiarrhea, the latter being the most common.[20]Hypersensitivity reactions include skin rashes,urticaria,fever, andanaphylaxis.[4]Pseudomembranous colitis andClostridioides difficile have been reported with use of cefalexin.[4] Less common and more serious side effects include bruising of the skin and yellowing of the skin or eye whites.[21]
Signs and symptoms of anallergic 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.[22]
Like otherβ-lactam antibiotics, renal excretion of cefalexin is delayed byprobenecid.[4] It is also not recommended to take cefalexin withdofetilide, liveCholera vaccine,warfarin, andcholestyramine.[23]Alcohol consumption reduces the rate at which it is absorbed.[24] Cefalexin also interacts withmetformin, anantidiabetic drug,[4] and this can lead to higher concentrations of metformin in the body.[4][25]Histamine H2 receptor antagonists likecimetidine andranitidine may reduce theefficacy of cefalexin by delaying itsabsorption and altering its antimicrobialpharmacodynamics.[26] Zinc and zinc supplements also interact with cefalexin and may reduce the amount of cefalexin in the body.[21]
Cefalexin is a β-lactam antibiotic of the cephalosporin family.[27] It isbactericidal and acts by inhibiting synthesis of thepeptidoglycan layer of the bacterial cell wall.[28] As cefalexin closely resembles d-alanyl-d-alanine, an amino acid ending on the peptidoglycan layer of the cell wall, it can irreversibly bind to the active site ofPBP, which is essential for the synthesis of the cell wall.[28] It is most active againstgram-positive cocci, and has moderate activity against somegram-negative bacilli.[4] However, some bacterial cells have the enzymeβ-lactamase, which hydrolyzes the β-lactam ring, rendering the drug inactive. This contributes toantibacterial resistance towards cefalexin.[29]
Cefalexin is rapidly and almost completely absorbed from thegastrointestinal tract withoral administration.[30] Absorption is slightly reduced when it is taken with food and the medication can be taken without regard for meals.[30] Peak levels of cefalexin occur about 1 hour after administration.[30] Maximal levels of cefalexin increase approximately linearly over a dose range of 250 to 1,000 mg.[30]
Like most other cephalosporins, cefalexin is notmetabolized or otherwise inactivated in the body.[26][31]
Theelimination half-life of cefalexin is approximately 30 to 60 minutes in people with normal renal function.[31][30] Therapeutic levels of cefalexin with oral administration are maintained for 6 to 8 hours.[30] More than 90% of cefalexin is excreted unchanged in the urine within 8 hours.[30]
It is on theWorld Health Organization's List of Essential Medicines.[14] The World Health Organization classifies cefalexin as highly important for human medicine.[32]
Cefalexin is theInternational Nonproprietary Name (INN) and theAustralian Approved Name (AAN), while cephalexin is theBritish Approved Name (BAN) and the United States Adopted Name (USAN).[33] Brand names for cefalexin include Keflex, Acfex, Cephalex, Ceporex, L-Xahl, Medoxine, Ospexin, Torlasporin, Bio-Cef, Panixine DisperDose, and Novo-Lexin.[34][35]
According to Plumb's Veterinary Medication Guides, cefalexin can be used in treating skin, respiratory tract, and urinary tract infections. Specifically, it can treatpyoderma in dogs.[36] 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.[37]
Cefalexin (Lexylan) is indicated for the treatment of cattle, dogs, and cats in the European Union.[2]
