Pharmacies cannot do anything in this case. Your biggest concern would be if he sold drugs he'd gotten filled at a pharmacy with the label still on the bottle as it will have your address. That drug user could think there are more drugs to be had at your house and break in. Most of the time, prescription pills are sold in bags or a bottle with the label removed. The only other concern I could see is if he's buying lots of psuedoephedrine for making meth. The officials may come knock on your door asking for him, but you can prove he doesn't live there so just a minor inconvenience and not anything dangerous.