Access to drug therapy and substitution between alternative antidepressants following an expansion of the California Medicaid formulary.

In May 1996, the California Medicaid Program (Medi-Cal) added two SSRI antidepressants to its formulary to facilitate the substitution of the SSRIs for older medications as clinically warranted, especially in minority patients thought to be particularly at risk for poor outcomes using older medications. Moreover, it was expected that the overall use of antidepressants would increase as patients who experienced sub-optimal outcomes prior to the formulary expansion would again seek treatment once new options were available. The formulary expansion did significantly alter the clinical treatment decision process, resulting in an immediate and sustained increase in the number of depressed patients initiating antidepressant therapy, primarily with the added SSRIs. This increase in SSRI use after the formulary expansion cannot be fully attributed to desired substitution effects, such as the narrowing of racial differences in SSRI use. However, while some expansion in overall antidepressant use may have been desired, the clinical validity of this expansion cannot be determined based on the results presented here.