What drove the diffusion of generic fluoxetine?
We found that greater differences in copayments between the generic and brand-name products were associated with greater use of the generic, consistent with a long literature demonstrating that financial incentives affect patients use of medications.12 However, even among patients with no difference in copayments between generic and brand-name fluoxetine, nearly two-thirds were either started on or switched to the generic preparation. This suggests that while consumer incentives may have played a role in driving the adoption of generic fluoxetine, other, broader forces were also at work. Current state regulations on generic substitution can provide one context for understanding this finding. In the eleven states in which pharmacists are required by law to substitute generic for brand-name products, only 31 percent of new fluoxetine prescriptions were filled for Prozac, largely because of “dispense as written” orders by physicians. In the remaining states, where laws permit but do not r
