Why isn't there some sort of nationally used pharmacy system?

I was thinking about all these ads on TV now for abuse of prescription drugs, and about all the episodes of Intervention (I’m a big fan) about people addicted to perfectly legal prescription pills, and I wondered why we can’t have some kind of system in place that is federally required for all pharmacies; a data base where you can see if that person, by SS or DOB or something, has filled a prescription anywhere in the country. That way, when people go to multiple doctors for the same prescriptions, they can’t simply go to different pharmacies to get them filled. It would almost completely eliminate the ability for people to legally obtain ridiculous amounts of medications.