mephenytoin vs antiepileptic

mephenytoin and antiepileptic both are nouns.

Word	Noun	Adjective	Verb	Adverb
mephenytoin	Yes	No	No	No
antiepileptic	Yes	No	No	No

As nouns, antiepileptic is a hypernym of mephenytoin; that is, antiepileptic is a word with a broader meaning than mephenytoin:

mephenytoin: a toxic anticonvulsant drug (trade name Mesantoin) used in the treatment of epilepsy when less toxic anticonvulsants have been ineffective
antiepileptic: a drug used to treat or prevent convulsions (as in epilepsy)

Other hypernyms of mephenytoin include anticonvulsant, anticonvulsant drug, antiepileptic drug.

mephenytoin (noun)	antiepileptic (noun)
a toxic anticonvulsant drug (trade name Mesantoin) used in the treatment of epilepsy when less toxic anticonvulsants have been ineffective	a drug used to treat or prevent convulsions (as in epilepsy)