phe·​nyt·​o·​in | \ fə-ˈni-tə-wən How to pronounce phenytoin (audio) \

Definition of phenytoin

: a crystalline anticonvulsant compound C15H12N2O2 used in the form of its sodium salt in the treatment of epilepsy

called also diphenylhydantoin

Examples of phenytoin in a Sentence

Recent Examples on the Web In the effluent from the Morgantown wastewater plant, the USGS team found high concentrations of three drugs in addition to phenytoin. Natasha Gilbert, STAT, "‘Dump it down the drain’: How contaminants from prescription-drug factories pollute waterways," 11 Dec. 2019 Three years later, Snyder, whose team tested both raw and drinking-water samples at 18 U.S. sites, added ibuprofen, meprobamate (an antianxiety medication), and phenytoin (another antiseizure drug), along with other pharmaceuticals, to the list. Rachael Moeller Gorman, Good Housekeeping, "Is Your Tap Water Safe?," 15 Aug. 2012

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'phenytoin.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of phenytoin

1941, in the meaning defined above

History and Etymology for phenytoin


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The first known use of phenytoin was in 1941

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Cite this Entry

“Phenytoin.” Dictionary, Merriam-Webster, Accessed 4 Mar. 2021.

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phe·​nyt·​o·​in | \ fə-ˈnit-ə-wən How to pronounce phenytoin (audio) \

Medical Definition of phenytoin

: an anticonvulsant used often in the form of its sodium salt C15H11N2NaO2 to prevent or treat seizures

called also diphenylhydantoin

— see dilantin

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