Hydroxychloroquine Sulfate (Hydroxychloroquine Sulphate) is a salt of hydroxychloroquine (HCQ, Plaquenil), a 4-aminoquinoline based antiviral drug. Synonyms: 7-Chloro-4-[4-(N-ethyl-N-b-hydroxyethylamino)-1-methylbutylamino]quinoline sulfate Molecular Formula: C18H26ClN3O · H2SO4 …