Utilization Patterns of Antidepressant Medications in a Patient Population Served by a Primary Care Medical Group

OBJECTIVE: To assess utilization patterns of different antidepressants in patients served by a primary care medical group. DESIGN: Prescription claims from two third-party insurers in Southern California were retrospectively analyzed in order to identify all plan members with a pharmacy benefit who were using antidepressants. Prescription data covered two years-1995 and 1996. RESULTS: The patient sample included 177 (18.8%) patients who received fluoxetine as initial therapy, 98 (10.4%) sertraline, 175 (18.6%) paroxetine, 373 (39.6%) tricyclic antidepressants (TCAs), and 119 (12.3%) other antidepressants. The treatment completion rate (i.e., adequate dose and duration according to Agency for Health Care Policy and Research guidelines) was fluoxetine 18.6%, sertraline 14.3%, paroxetine 6.9%, TCAs 3%, and other antidepressants 7.6%. All the pairwise comparisons vs. fluoxetine were statistically significant, except for sertraline. The overall switch rate ranged from 5.6% for TCAs to 13.7% for paroxetine. No difference in augmentation rate was found among selective serotonin reuptake inhibitors (fluoxetine 6.8%, sertraline 4.1 %, paroxetine 5.7%), while the augmentation rate for fluoxetine was significantly higher than for TCAs (6.8% vs. 1.9%, p less than 0.01). The titration rate for the first three refills was 20.3% for fluoxetine, 28.1 % for sertraline, 21.9% for paroxetine, 40.2% for TCAs, and 33.3% for other antidepressants (difference between TCAs and fluoxetine was significant at p less than 0.01). CONCLUSION: Data demonstrated significant differences in antidepressant utilization patterns among patients treated in this primary care medical group. The lack of effective dosing and duration of antidepressant treatment in this population is consistent with previous research.