Utilization of and expenditures for selective serotonin reuptake inhibitors (SSRIs) and factors associated with change in price per-prescription of brand SSRIs in the Texas Medicaid programme (1991-2009)

Abstract

Objectives To assess: (1) the utilization of and expenditures for selective serotonin reuptake inhibitors (SSRIs); and (2) the association of events such as generic entries, reformulation entries and new indication approvals with the change in brand SSRI price per-prescription reimbursed (PPPR) in the Texas Medicaid health programme, USA. Methods The Texas Medicaid summary database, containing quarterly data on utilization (number of prescriptions dispensed) and expenditure (US dollar amount reimbursed) for medications between the first quarter of January 1991 and last quarter of December 2009, was used. Annual measures of SSRI utilization and expenditures were reported. Time-series intervention analysis was conducted with the log-transformed ratio (current-to-previous quarter) of brand SSRI PPPR as the dependent variable and specified events (generic entry, reformulation entry and new indication approval) as the independent variables. Key findings The annual utilization of the entire SSRI class of therapy among Texas Medicaid beneficiaries increased by more than 20-fold from 1991 to 2004 (35 933 to 819 952 prescriptions), and then decreased from 2005 to 2008 (779 540 to 183 154 prescriptions). In 2009, the number of SSRI prescriptions increased to 413 103 prescriptions. The annual expenditures for SSRIs followed the same pattern as the utilization measures. For a majority of brand SSRIs, none of the events (noted above) were found to be significantly associated with change in PPPR. Conclusions Annual utilization and expenditures of SSRIs varied over time. For a majority of brand SSRIs, generic entries, reformulation entries and new indication approvals were not related to change in PPPR.