Prevalence and patterns of concomitant use of selective serotonin reuptake inhibitors and other antidepressants in a high-cost polypharmacy cohort.

Background: Concomitant antidepressant therapy for patients who do not respond to selective serotonin reuptake inhibitors (SSRIs) may be appropriate under close medical supervision. However, little is known about the prevalence or patterns of concurrent antidepressant therapy in a typical large health maintenance organization.

Objective: The purpose of this study was to determine the prevalence of concomitant SSRI-antidepressant therapy and to assess the relationship between concomitant SSRI therapy, patient demographic characteristics, and the use of multiple prescribers and pharmacies.

Methods: This was a retrospective analysis of administrative prescription and medical claims data from January 1998 through September 1999. Data were obtained on beneficiaries who had >15 prescriptions dispensed in either of the first 2 quarters of 1999 and/or patients who accrued >$1,000 in prescription costs in either or both of the quarters. Patients were defined as undergoing concomitant SSRI therapy if they had received > or = 14 days of concomitant treatment with 2 SSRIs, an SSRI and tricyclic antidepressant, an SSRI and benzodiazepine, or an SSRI and miscellaneous antidepressant. Contingency analysis and logistic regression were used to identify factors associated with concomitant SSRI therapy.

Results: The relative risk for concomitant SSRI-SSRI therapy for patients with multiple prescribers versus a single prescriber was 2.32; the relative risk for patients receiving prescriptions from multiple pharmacies versus a single pharmacy was 2.97. Female patients were 19.8% more likely than male patients to receive concomitant SSRI therapy. Use of multiple prescribers increased the odds for concomitant SSRI therapy by >3.0 across the 4 therapeutic combinations. Use of multiple pharmacies increased the odds for concomitant SSRI-SSRI therapy by 5.42.

Conclusions: Prescription of concomitant SSRI therapy was strongly associated with changes in strength of dosage and products and with use of multiple prescribers and pharmacies.