Background: A great deal of previous work on the pharmacoeconomics of alcohol, tobacco and illicit drug abuse indicates that as cost decreases, abuse increases and vice versa. The application of these cost principles to the abuse of prescribed medications is largely unknown. In this paper we assessed whether the introduction of generic products in the U.S. increased the therapeutic use and illicit abuse of extended release oxycodone products and the fentanyl patch.
Methods: As an index of therapeutic use, we purchased prescription data for each of the ZIP codes in which we had corresponding abuse data. To gather information about prescription drug abuse, we elicited cases with quarterly questionnaires completed by a key informant network.
Results: The introduction of generic extended release (ER) oxycodone and fentanyl patch did not significantly change the total prescriptions written for these products, but markedly altered the composition of sales: branded sales dropped precipitously over a very short time and this was compensated for by a corresponding increase in sales of generics. Surprisingly, the introduction of generic products did not increase the abuse of ER oxycodone or fentanyl products; the branded version was the drug of choice for at least 2 years.
Conclusions: Our data suggest that drug costs alone do not increase the overall likelihood that a prescription opioid analgesic will be used therapeutically or abused. However, while generics are rapidly endorsed by insurance companies as a prescribed entity, abuse of the branded versions of ER oxycodone and fentanyl remains predominant for some time.