Discontinuation rates and health care costs in adult patients starting generic versus brand SSRI or SNRI antidepressants in commercial health plans

Abstract

Background: Generic antidepressants offer significant prescription drug cost savings compared with brand-name antidepressants, but critics of managed care interventions promoting generic medication use suggest that some generic antidepressants are not as safe or effective as the brand alternatives.

Objective: To assess (a) rates of discontinuation of the initially dispensed medication and (b) disease-specific and total health care costs and pharmacy costs, comparing patients who initiated therapy with brand versus generic selective serotonin reuptake inhibitors (SSRI) or selective norepinephrine reuptake inhibitors (SNRI).

Methods: Antidepressant users aged 18 to 64 years with no pharmacy claims for an SSRI/SNRI in the 180 days prior to the start of SSRI/SNRI therapy (baseline) were identified in the MarketScan database between July 1, 2005, and June 30, 2007, and were followed for 180 days (followup). All study patients met the following criteria: (a) continuously eligible from baseline through follow-up; (b) at least 1 medical claim with a primary or secondary diagnosis of major depressive disorder (ICD-9-CM codes 296.2 or 296.3) in either the baseline or follow-up period; and (c) no pharmacy claims for antipsychotic medications in the baseline period. For brand versus generic antidepressant initiators, logistic regression was used to determine the odds of 6-month therapy discontinuation, defined as no medication refills or absence of a refill for the initially dispensed medication within 1.5 times the days supply dispensed, adjusted for important covariates. Costs were measured as total plan allowed charges including member cost share. Adjusted mean (least squares means holding covariates at mean values) all-cause medical costs, disease-specific (claims with a ICD-9-CM diagnosis code for major depressive disorder in the primary or secondary diagnosis field) medical costs, all-cause pharmacy costs, and SSRI/SNRI antidepressant costs were compared for brand versus generic initiators using generalized linear regression models, also adjusted for baseline covariates.

Results: Of 16,659 new SSRI/SNRI users, 47.8% (n=7,955) initiated a brand-name medication and 52.2% (n=8,704) initiated a generic product. Of the 7,955 who initiated a brand-name antidepressant, 46.8% (n=3,723) discontinued the initially dispensed drug within 180 days, compared with 44.2% (n=3,843) of the 8,704 who initiated a generic. The adjusted odds of discontinuation among generic and brand drug users did not significantly differ (odds ratio [OR]=1.09, 95% CI=0.98-1.22). Adjusted all-cause 6-month average health care costs in patients initiating therapy on a generic antidepressant were $3,660 (95% CI=$3,538-$3,787) compared with $4,587 (95% CI=$4,422-$4,757) for patients initiating on a brand-name antidepressant. Adjusted average 6-month SSRI/SNRI antidepressant costs were 43.7% lower in patients initiating on a generic drug ($174 vs. $309).

Conclusions: The likelihood of discontinuation was similar for patients who initiated therapy with brand or generic antidepressants, and shortterm health care costs and pharmacy costs were lower in patients starting a generic SSRI/SNRI. The results suggest that the use of generic antidepressants as first-line agents in the treatment of major depressive disorder is associated with continuation rates similar to initiation with brand antidepressants but with lower health care costs.