Economic outcomes with antidepressant pharmacotherapy: a retrospective intent-to-treat analysis

Herein we describe a retrospective intent-to-treat evaluation designed to compare the natural course of antidepressant utilization and direct health service expenditures for the treatment of a single episode of major depression among patients enrolled in a multistate network-model health maintenance organization and initially prescribed either a tricyclic antidepressant (amitriptyline or nortriptyline) or the serotonin selective reuptake inhibitor (SSRI) fluoxetine. Patient-level paid-claims data for the period July 1, 1988, through December 31, 1991, were abstracted. During the above time frame, fluoxetine was the only SSRI available in the United States. Patients prescribed amitriptyline were more than three times as likely to require a change in antidepressant pharmacotherapy (OR = 3.27, 95% CI = 2.31 to 5.49), while patients prescribed nortriptyline were nearly four times more likely to change medication (OR = 3.82, 95% CI = 2.74 to 6.83) relative to patients initially prescribed fluoxetine. Consistent with our intent-to-treat design, all accrued health service expenditures were assigned to the pharmacotherapeutic option initially prescribed. Multivariate analyses revealed that initiation of antidepressant pharmacotherapy with amitriptyline resulted in a 25.7% increase in per capita depression-related health service expenditures per year, while initiation of antidepressant pharmacotherapy with nortriptyline resulted in a 28.1% increase in per capita depression-related health service expenditures per year relative to patients initially prescribed fluoxetine. A financial break-even point was achieved at the conclusion of Month 5, at which time all three intent-to-treat cohorts had comparable health service expenditures in total. From a financial perspective, results stemming from this inquiry suggest that the initiation of antidepressant pharmacotherapy with an SSRI is warranted.