"What’s the painkiller equivalent of GNC?"
Painkillers are a highly regulated market. Even the Sackler family had to work the system to make their ill-gotten profits.
Vitamins are not. Indeed, the highly criticized Dietary Supplement Health and Education Act of 1994, co-sponsored by Senator Orrin Hatch (in turn receiving financial support from supplement manufacturers), made vitamins and other dietary supplements far less scrutinized by the FDA than pain killers.
The vitamin advertisements are "so much more creative than the painkiller ones" because the painkiller ones get to say "we kill pain" while being restricted from broader claims, while the vitamin advertisements have to work to imply unproven health benefits.
There is no painkiller equivalent of GNC because the more effective pain killers require a prescription for legal sale, and a trained pharmacist on staff to oversee sales.
If you can make and sell OxyContin, then as the Sackler family shows, you can make bank.
It's time for the metaphor to die because it encourages making software which is equally as addictive as OxyContin. And we see that's happened.
Also, magnesium is not a vitamin, so if "vitamins" is extended to include other food supplements than I'll point out alcohol and marijuana are also used as painkillers and antidepressants, and there's a big underground market for opioids.
If you'll excuse me, I've got to pop over to the druggist to get some OTC cocaine toothache drops. https://collections.nlm.nih.gov/catalog/nlm:nlmuid-101400866...
