Are you sure? Naproxen is the generic chemical component, not a brand´s name.
For instance, Ibuprofen is the pharmacological component, while Tylenol is the brand made by Pfizer. There are dozens of companies making Naproxene under their own exclusive brand. Is this still copyright infringement? Who owns the pharmacological/chemical component name used by all pharma companies ?
You're wrong as you're making the wrong assumption.
Such chemicals names are always branded. Chemicals are not "naproxen" but something like "1-butyl-2,3-whatever-goes-here". For example Teflon is a similar brand (heavily guarded by Dupont, got their cease and desist in the past, thank you very much), but the chemical is PTFE - short for polytetrafluorethylene.
Naproxen is a brand and registered by multiple owners, either as such or in combinations, all under class 5 pharmaceuticals. The owner might be different depending on country.
Again, copyright infringement.
Edit: I deal in plastics, which are chemicals, so I know a bit about this.
Sometimes the original owner is not holding the name anymore. For example BAKELITE is a brand that is long expired since it has been discovered at the beginning of the century. However it has been later picked up by several firms depending on country and again it is still a brand everywhere. And is still a valid, legally enforceable brand.
A brand legal adviser could explain more of such intricacies.