"In conclusion, patterns of prescription drug misuse among high-risk young adults in LA and NY appear to conform to and be shaped by differences in local markets for illicit drugs in each city. Our findings indicate that current misuse of prescription drugs in both cities encompasses a broad range of practices, such as sniffing, injecting, polydrug use, and drug substitution, and involves frequent misuse of illicit substances. Initiation into prescription drug misuse was often preceded by being prescribed one or more types of prescription drugs, which was then followed by initiating illicit drugs with similar psychotropic effects."

Source

Lankenau, Stephen E.; Schrager, Sheree M.; Silva, Karol; Kecojevic, Alex; Bloom, Jennifer Jackson; Wong, Carolyn; and Iverson, Ellen, "Misuse of prescription and illicit drugs among high-risk young adults in Los Angeles and New York," Journal of Public Health Research (Pravia, Italy: February 14, 2012) Vol 1, No 1, p. 29.
http://www.jphres.org/index.p…