Mylanta vs gastric antacid

Mylanta and gastric antacid both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mylanta	Yes	No	No	No
gastric antacid	Yes	No	No	No

As nouns, gastric antacid is a hypernym of Mylanta; that is, gastric antacid is a word with a broader meaning than Mylanta:

Mylanta: an antacid
gastric antacid: an agent that counteracts or neutralizes acidity (especially in the stomach)

Other hypernyms of Mylanta include alkaliser, alkalizer, antacid, antiacid.

Mylanta (noun)	gastric antacid (noun)
an antacid	an agent that counteracts or neutralizes acidity (especially in the stomach)