1) what the hell does this have to do with bitcoin or any other cryptocurrency? It's just a centralized service that uses basic cryptography. Why would people trust your service? it can be hacked, your internal database modified, etc.
It's bitcoin addresses that are logged and so the association with cryptocurrency, we take every security precaution, master keys are not stored, subkey addresses are hashed, etc.
2) Are you seriously expecting people to print (and scan!) QR codes on individual pills? Really?
No, that would be silly, the pills are so numerous for a start that people wouldn't bother to scan them on a regular basis. I suspect the bottle would be more sensible. The image gets the idea across quite nicely though.
3) Finally, what is stopping some asshole from taking a pill from a bottle and replacing it with another pill with the same code?
Well that's a murderer and there's no stopping him.
Like, I don't want to be mean, but this is among the dumbest ideas I've ever heard.
I think it could be useful actually for any business who cared to participate. Nobody can be forced to use the service.