"States with PDMPs [prescription drug monitoring programs] have experienced considerable reductions in the time and effort required by law enforcement and regulatory investigators to explore leads and the merits of possible drug diversion cases. The presence of a PDMP helps a state reduce its illegal drug diversion, but diversion activities may increase in contiguous states without PDMPs."
Source
General Accounting Office, "Prescription Drugs: State Monitoring Programs Provide Useful Tool to Reduce Diversion" (Washington, DC: Government Printing Office, May 2002), GAO-PO-634, p. 15.
http://www.gao.gov/new.items/…
