Drug Expenditure, Price, and Utilization in the U.S. Medicaid: A Trend Analysis for SSRI and SNRI Antidepressants from 1991 to 2018.

Background: SSRIs and SNRIs are antidepressants that have largely substituted old antidepressants like Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs). They have been widely used since 1987 when the FDA approved the first SSRI Fluoxetine and the first SNRI Venlafaxine in 1993. Since then, several new SSRIs and SNRIs have been approved and entered the market. Utilization, pricing, and spending trends of SSRIs and SNRIs have not been analyzed yet in Medicaid.

Aim: To assess the trends of drug expenditure, utilization, and price of SSRI and SNRI antidepressants in the US Medicaid program, and to highlight the market share of SSRIs and SNRIs and the effect of generic drug entry on Medicaid drug expenditure.

Methods: A retrospective descriptive data analysis was conducted for this study. National pharmacy summary data for study brand and generic drugs were retrieved from the Medicaid State Outpatient Drug Utilization Data. These data were collected by the US Centers for Medicare and Medicaid Services (CMS). The study period was between 1991 and 2018. Study drugs include 12 different SSRI and SNRI brands and their generics available in the market, such as citalopram, escitalopram, paroxetine, fluoxetine, sertraline, venlafaxine, desvenlafaxine, duloxetine, and levomilnacipran. Data were analyzed annually and categorized by total prescriptions (utilization), total reimbursement (spending), and cost per prescription as the proxy of the price for each drug.

Results: From 1991 to 2018, total prescriptions of SSRI and SNRI drugs rose by 3001%. Total Medicaid spending on SSRIs and SNRIs increased from USD 64.5 million to USD 2 billion in 2004, then decreased steadily until it reached USD 755 million in 2018. The SSRIs average utilization market share was 87% compared to 13% of the SNRIs utilization market share. About 72% of total Medicaid spending on the two groups goes to SSRIs, while the remaining 28% goes to SNRIs. Brand SSRIs and SNRIs prices increased over time. On the contrary, generic drugs prices steadily decreased over time.

Discussion: An increase in utilization and spending for both SSRI and SNRI drugs was observed. After each generic drug entered the market, utilization shifted from the brand name to the respective generic due to their lower price. These generic substitutions demonstrate a meaningful cost-containment policy for Medicaid programs.

Implications for health policies: Our findings show the overall view of Medicaid expenditure on one of the most commonly prescribed drug classes in the US. They also provide an important insight toward the antidepressant market and the importance of monitoring different drugs and their alternatives.