Oregon made pseudoephedrine-based cold medicines prescription-only back in 2006. A new report on the effectiveness in reducing the availability of P concludes:
Oregon’s experience with methamphetamine manufacture and abuse since 2006 does not stand out from its neighbors or other parts of the United States. This potentially calls into question whether Oregon’s Rx-only law had any independent effect on these key measures. Moreover, this law does come at some cost to consumers and government and private payers.
So the ban on selling effective cold medicine over the counter had no observable effect upon the P problem, but does cause inconvenience for people with a cold. It will be interesting to see comparable studies for New Zealand in a few years time, although the lack of neighbouring states makes it harder to find control groups to compare with.