The same stores sell completely ineffective homeopathic "medicines" alongside real medicines already. There are no signs. Its already up to the consumer to determine what may or may not actually work at the pharmacy.
I spent my money on a product sold by a pharmacy that is quite literally a scam. I'm naturally a skeptical person, but I didn't think I needed to independently check whether what's on a pharmacy store's shelves is medicine or a scam. That's not my lane, I trusted that the pharmacy would only sell medicine that works.