ABSTRACT Objective: Adjunctive therapy is often used for treatment of major depressive disorder (MDD) following an inadequate response to an antidepressant. However, there is little information regarding its practice within primary care in the United Kingdom (UK). Objectives of the study were to examine incidence and predictors of adjunctive pharmacotherapy among patients with MDD treated with selective serotonin reuptake inhibitors (SSRIs) by UK general practitioners (GPs). Methods: The General Practice Research Database was used to identify 15,274 MDD patients prescribed first-line treatment with SSRIs from 2006-2008 (latest patient follow-up towards end of 2010). Treatment trajectories were identified and classified as adjunctive therapy, combination therapy, drug switches, dose increases, and restart of therapy. Incidence and predictors of adjunctive therapy were assessed, and healthcare resource utilization was evaluated. Results: Overall incidence of adjunctive therapy was 3.07/100 person years (95% CI 2.90-3.25). Patients prescribed adjunctive therapy were more likely to be female (IRR 1.15, p = 0.03), of higher age (IRRs 1.51-2.60, p ≤ 0.001), and had a greater depression severity score (IRR 1.02, p = 0.003). Presence of irritable bowel syndrome (IRR 1.53, p = 0.001), and an increasing Charlson Comorbidity Index (IRR 1.15, p = 0.01) were associated with a higher incidence of adjunctive therapy. MDD-related general practitioner consultations among patients who received adjunctive therapy was lower compared with patients receiving other treatment interventions (IRRs 0.79 - 0.87, p ≤ 0.001). Conclusions: Adjunctive therapy is infrequently utilized relative to other treatment options for management of MDD among patients who are inadequate responders to their SSRI treatments in UK primary care; however some groups are more likely to receive adjunctive therapy than others.
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