Antidepressant switching patterns in the treatment of major depressive disorder: a General Practice Research Database (GPRD) Study

AIMS: To investigate switching patterns of major antidepressant treatments and associated factors in a primary care adult population with major depressive disorder (MDD) using data from the General Practitioner Research Database (GPRD). METHODS: A retrospective cohort study was conducted using the GPRD. The study included patients with MDD, aged [18-70], with a new prescription for amitriptyline, citalopram, escitalopram, fluoxetine, paroxetine, sertraline or venlafaxine between January 1, 2001 and September 30, 2003 and having no antidepressant prescription in the 6 months preceding index date. Switching of antidepressant treatment was defined as a prescription of a different antidepressant among all available marketed antidepressant treatment at this time (no restriction of compound) from 1 month before up to 2 months after the calculated end of the previous antidepressant treatment. Survival analysis techniques were used to describe switching of antidepressant and time to switch. Profiles of switchers were described and by-treatment analyses performed. RESULTS: Data from over 59,000 patients showed that 16% switched antidepressants. Seventy-two per cent of switches appeared within 3 months after treatment initiation. Within switchers, median time to switch was 53 days. Switching patients had generally a more severe psychiatric profile, including more previous episodes of depression or other psychiatric disorders. They also had a higher proportion of concurrent psychiatric disorders (especially anxiety) and concomitant prescription of anxiolytics or hypnotics. Patients initially prescribed amitriptyline were almost twice as likely to switch (27%) as patients prescribed venlafaxine (17%) or an SSRI (15%). CONCLUSIONS: This population-based study confirmed that antidepressant switch is more likely to occur within the first 3 months of treatment and in patients with a more severe psychiatric profile. A particular attention paid to these patients within the early phase of treatment may therefore help to improve their management.