{{medical}}
{{drugbox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 457457901
| IUPAC_name = 5,5-diphenylimidazolidine-2,4-dione
| image = Phenytoin structure.svg
| alt = Structural formula of phenytoin
| width = 150
| image2 = Phenytoin 3D ball.png
| alt2 = Ball-and-stick model of the phenytoin molecule
| width2 = 160
<!--Clinical data-->
|pronouce = {{IPAc-en|ˈ|f|ə|n|ɪ|t|oʊ|ɨ|n}}
| tradename = Dilantin, Phenytek, others<ref name=AHFS2015/>
| Drugs.com = {{drugs.com|monograph|phenytoin}}
| MedlinePlus = a682022
| pregnancy_AU = D
| pregnancy_US = D
| legal_AU = S4
| legal_CA = Rx-only
| legal_UK = POM
| legal_US = Rx-only
| routes_of_administration = 口服，[[wikt:Parenteral|腸道外]]
<!--Pharmacokinetic data-->
| bioavailability = 70-100% (口服)，24.4%（直肠和静脉注射）
| protein_bound = 95%<ref name=AHFS2015/>
| metabolism = [[肝臟]]
| onset = 10 to 30 分鐘（靜脈注射）<ref name=Ros2010/>
| elimination_half-life = 10–22小時<ref name=AHFS2015/>
| duration_of_action= 24小時<ref name=Ros2010>{{cite book|last1=Marx|first1=John A.|title=Rosen’s emergency medicine : concepts and clinical practice|date=2010|publisher=Mosby/Elsevier|location=Philadelphia|isbn=9780323054720|page=1352|edition=7|url=https://books.google.ca/books?id=u7TNcpCeqx8C&pg=PA1352}}</ref>
| excretion = 主要透過膽道、泌尿道
<!--Identifiers-->
| IUPHAR_ligand = 2624
| CAS_number_Ref = {{cascite|correct|??}}
| CAS_number = 57-41-0
| ATC_prefix = N03
| ATC_suffix = AB02
| ATC_supplemental =
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 8107
| PubChem = 1775
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB00252
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 1710
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 6158TKW0C5
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D00512
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 16
<!--Chemical data-->
| C=15 | H=12 | N=2 | O=2
| molecular_weight = 252.268 g/mol
| smiles = O=C2NC(=O)NC2(c1ccccc1)c3ccccc3
| InChI = 1/C15H12N2O2/c18-13-15(17-14(19)16-13,11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10H,(H2,16,17,18,19)
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/C15H12N2O2/c18-13-15(17-14(19)16-13,11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10H,(H2,16,17,18,19)
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = CXOFVDLJLONNDW-UHFFFAOYSA-N
}}
<!-- Definition and medical uses -->
’’’苯妥英’’’（{{lang|en|Phenytoin}}，或稱diphenyl hydantoin），常見商品名’’’大仑丁’’’（Dilantin），是一种{{tsl|en|anticonvulsant|抗驚厥藥物}}<!-- <ref name=AHFS2015/> -->。該藥在治療[[强直－阵挛性发作]]及{{tsl|en|partial seizure|部份癲癇發作|部份發作}}有效果，但無法治療{{tsl|en|absence seizure|失神性癲癇發作|失神性發作}}<!-- <ref name=AHFS2015/> -->。苯妥英能藉由口服或靜脈注射給藥<!-- <ref name=AHFS2015/> -->，當[[癲癇重積狀態]]發生時，可藉由靜脈注射給予苯妥英，相對的[[苯二氮䓬类]]無法治療該症狀<!-- <ref name=AHFS2015/> -->。該藥也可治療特定的[[心律不整]]及{{tsl|en|neuropathic pain||神經病變性疼痛}}<ref name=AHFS2015/>。靜脈注射給藥通常會於30分鐘內開始作用，藥效可維持24小時<ref name=Ros2010/>，注射後可進行濃度監測以維持適當濃度<ref name=AHFS2015/>。
<!-- Side effects -->
常見副作用包含噁心、胃痛、缺乏食慾、肢體協調不良、[[多毛症|毛髮增長]]，以及牙齦增生<!-- <ref name=AHFS2015/> -->。其他可能的嚴重副作用則包含{{tsl|en|sleepiness||嗜睡}}、[[自残]]、肝臟問題、[[骨髓抑制]]、[[低血壓]]，以及{{tsl|en|toxic epidermal necrolysis|毒性表皮溶解症}}<!-- <ref name=AHFS2015/> -->。有證據顯示妊娠期間服用該藥物可能對胎兒造成不良影響<!-- <ref name=AHFS2015/> -->，[[母乳餵養|哺乳]]期間用藥目前沒有相關風險顯示<!-- <ref name=AHFS2015/> -->。服藥期間並用[[乙醇]]可能干擾藥效<ref name=AHFS2015/>。
<!-- History, society, and culture -->
苯妥英最早於1908年被製造，並於1936年發現其對於癲癇的作用<ref>{{cite book|last1=Aicardi|first1=Jean|title=Epilepsy : a comprehensive textbook|date=2008|publisher=Wolters Kluwer Health/Lippincott Williams & Wilkins|location=Philadelphia|isbn=9780781757775|page=1431|edition=2nd ed.|url=https://books.google.ca/books?id=3ZktoDp7tZoC&pg=PA1431}}</ref>。該藥列名於[[世界卫生组织基本药物标准清单]]之中，為基礎醫療體系必備藥物之一<ref>{{cite web|title=WHO Model List of Essential Medicines|format=PDF|url=http://apps.who.int/iris/bitstream/10665/93142/1/EML_18_eng.pdf?ua=1|work=World Health Organization|accessdate=22 April 2014|date=October 2013}}</ref>。苯妥英目前為學名藥，價格不貴<ref name=Ric2013>{{cite book|last1=Hamilton|first1=Richard J.|title=Tarascon pocket pharmacopoeia.|date=2013|publisher=Jones & Bartlett Learning|location=Burlington, MA.|isbn=9781449673635|page=294|edition=14|url=https://books.google.ca/books?id=Ti4xt1-9fLkC&pg=PA294}}</ref>。批發價約為每劑0.003至0.15美金之間<ref name=ERC2015>{{cite web|title=Phenytoin|url=http://erc.msh.org/dmpguide/resultsdetail.cfm?language=english&code=PNT100T&s_year=2014&year=2014&str=100%20mg&desc=Phenytoin&pack=new&frm=TAB-CAP&rte=PO&class_code2=05%2E&supplement=&class_name=%2805%2E%29Anticonvulsants%2Fantiepileptics%3Cbr%3E|website=International Drug Price Indicator Guide|accessdate=23 August 2015}}</ref> A month of treatment is about 30 USD in the United States.<ref name=AHFS2015>{{cite web|title=Phenytoin|url=http://www.drugs.com/monograph/phenytoin.html|publisher=The American Society of Health-System Pharmacists|accessdate=Aug 22, 2015}}</ref>。