Changes in prescription habits with the introduction of generic fluoxetine.

When the patent on fluoxetine expired in 2001, prices for it fell sharply and marketing decreased. We investigated how market share for fluoxetine changed with the introduction of the generic. Prescribing information was tracked at a military hospital where providers knew the cost of medication, but were not compelled to use the cheaper form. Market share for fluoxetine among selective serotonin reuptake inhibitors was observed for the 64 months surrounding the introduction, and changes were examined by linear regression analysis. Results showed that in the 32 months before the introduction of the generic, fluoxetine maintained a relatively steady share of prescriptions. After the introduction of the generic, fluoxetine steadily lost market share over time. No significant relationship could be seen between drug company visits and gains for their individual products. Examination of all Department of Defense prescriptions for the 16 months surrounding the introduction of generic fluoxetine showed a similar drop in its market share.