{{Drugbox
| Watchedfields = changed
| verifiedrevid = 457630940
| IUPAC_name = (7R)-3-Methyl-7- (α- D -phenylglycylamino) -3-cephem-4-carboxylic acid monohydrate
| image = Cefalexin.svg
| image2 = Cefalexin ball-and-stick.png
<!--臨床資料-->
| tradename = Keflex, Cepol, Ceporexine, Ceporex[1]
| Drugs.com = {{Drugs.com|monograph|Cephalexin}}
| MedlinePlus = a682733
| pregnancy_AU = A
| pregnancy_US = B
| legal_AU = S4
| legal_UK = POM
| legal_US = Rx-only
| routes_of_administration = Oral
| licence_US = Keflex
<!--藥理動力學資料-->
| bioavailability = Well absorbed
| protein_bound = 15%
| metabolism = 80% excreted unchanged in urine within 6 hours of administration
| elimination_half-life = For an adult with normal renal function, the serum half-life is 0.5–1.2 hours[2]
| excretion = [[Kidney|Renal]]
<!--列管編號-->
| CASNo_Ref = {{cascite|correct|CAS}}
| CAS_number_Ref = {{cascite|correct|??}}
| CAS_number = 15686-71-2
| ATC_prefix = J01
| ATC_suffix = DB01
| ATC_supplemental = {{ATCvet|J51|DB01}}
| PubChem = 2666
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB00567
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 25541
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 5SFF1W6677
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D00263
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 3534
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 1727
<!--化學資料-->
| C=16 | H=17 | N=3 | O=4 | S=1
| molecular_weight = 347.39 g/mol
| smiles = O=C2N1/C(=C(\\CS[C@@H]1[C@@H]2NC(=O)[C@@H](c3ccccc3)N)C)C(=O)O
| InChI = 1/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
| InChIKey = ZAIPMKNFIOOWCQ-UEKVPHQBBS
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 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
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = ZAIPMKNFIOOWCQ-UEKVPHQBSA-N
| melting_point = 326.8
}}
Cefalexin (INN, BAN) or cephalexin (USAN, AAN) is an antibiotic useful for the treatment of a number of bacterial infections. It is taken by mouth and is active against gram positive bacteria and some gram negative bacteria.[3] It is in the class of first generation cephalosporins and has similar activity to other agents within this group including the intravenous agent cefazolin.[4]
’’’頭孢氨芐’’’（{{lang-en|Cefalexin或Cephalexin}}，又譯’’’先锋霉素Ⅳ’’’、又作’’’賜福力欣’’’、’’’頭孢力欣’’’、’’’賜爾復新’’’、’’’西華烈信’’’、’’’施華林’’’、’’’喜化幸’’’、’’’雪華力欣、或’’’賜泛立信’’’等[0]）。是一种半合成的第一代口服[[頭孢菌素|头孢霉素类]]類[[抗生素]]药物，可用於數種細菌感染的[[抗細菌藥|抗生素]]。頭孢氨芐是口服藥，抗菌範圍包括[[革蘭氏陽性菌]]和部分[[革蘭氏陰性菌]][3]。頭孢氨芐屬於[[頭孢菌素#第一代|第一代頭孢菌素]]，它與其他同類的抗生素如靜脈施打的[[頭孢唑啉]]具有相似的作用[4]。
<!-- Medical uses -->
Cefalexin is used to treat a number of bacterial infections including: middle ear infections, strep throat, bone and joint infections,pneumonia, skin infections, and urinary tract infections. It may be used to prevent bacterial endocarditis. It is not effective againstmethicillin-resistant Staphylococcus aureus. It may be used in those who have mild or moderate allergies to penicillin but is not recommended is those with severe allergies. It has no effect against viral infections.[3]
<!-- 醫療用途 -->
頭孢氨芐被以於治療[[中耳炎]]、[[鏈球菌性咽炎]]、[[肺炎]]、骨與關節感染、[[蜂窩性組織炎]]、以及[[泌尿道感染]]等，它也可以被用於預防{{link-en|感染性心內膜炎|infective endocarditis}}。頭孢氨芐對於[[抗藥性金黃色葡萄球菌]]沒有效果。頭孢氨芐可以使用在對青黴素有輕微至普通程度過敏反應的病人身上，但對於有強烈過敏反應的病人而言則不適合使用。頭孢氨芐對{{link-en|病毒感染|viral disease}}並沒有效果[3]。在台灣，由於組織穿透性不佳以及抗藥性菌株較多，除蜂窩性組織炎及經確認菌株無抗藥性的泌尿道感染[18]仍使用頭孢氨芐作首選治療藥物，上述其他病症（中耳炎[12]、咽炎[13]、肺炎[14]、骨與關節感染[15]、以及感染心內膜炎[16]）已經建議使用其他抗生素治療[17]。
<!-- Side effects -->
Possible side effects include: allergies, stomach and intestinal upset, and Clostridium difficile diarrhea among others.[3] It ispregnancy category B in the United States and category A in Australia meaning that there is no evidence of harm after being taken by many pregnant women.[3][5] Use during breast feeding is okay.[6] It is suitable for use in children and those over 65 years of age. Doses may need to be decrease in those with kidney problems.[3]
<!-- 副作用 -->
頭孢氨芐的可能副作用包括[[過敏]]、腸胃不適、[[偽膜性結腸炎]]等等[3]。對於孕婦而言，本藥品在許多孕婦使用後仍沒有證據顯示它會對孕婦或胎兒造成傷害[3][5]（等同於美國的懷孕用藥等級B；與澳洲的等級A），在哺乳期間使用本藥品也是安全的[6]。兒童與65歲以上的老人都可以安全的使用本藥。[[腎功能衰竭|腎功能不佳]]的病人在使用本藥品時應依指示減少劑量[3]。
<!-- History, Society and Culture -->
In 2012, cefalexin was one of the top 100 most prescribed medications in the United States.[7] In Australia it is one of the 15 most prescribed medication.[8] It was introduced in 1969 and 1970 by a number of companies including Glaxo Wellcome and Eli Lilly and Company and was marketed as Keflex and Ceporex among others.[1][9] It is available as a generic drug under several other trade names and is not very expensive.[3][10] It is on the World Health Organization’s List of Essential Medicines, a list of the most important medication needed in a health system.[11]
<!-- 歷史、社會與文化 -->
2012年時頭孢氨芐名列美國前百大最常使用藥物[7]，在澳洲則躋身前十五強[8]。它在1969-1970年間由[[葛蘭素史克]]與[[禮來公司|禮來]]發現，並分別以’’’Keflex’’’與’’’Ceporex’’’為名上市[1][9]。今日，市面上已經有許多本藥品的[[通用名藥物|學名藥]]可供選擇，價格也不昂貴[3][10]。{{fact|常見的製劑有[[藥片]]、[[膠囊]]及口服藥水（或供配製成藥水的乾顆粒）}}。它也列名於[[世界衛生組織基本藥物標準清單]]上，這張清單列出世界衛生組織建議{{link-en|醫療系統|health system}}中應有的最重要的藥物[11]。