Prevalence and patterns of antidepressant switching amongst Primary Care patients in the UK

Objective: Non-response to antidepressant treatment is a substantial problem in Primary Care, and many patients with depression require additional second-line treatments. This study aimed to examine the prevalence and patterns of antidepressant switching in the UK, and identify associated demographic and clinical factors.

Method: Cohort analysis of antidepressant prescribing data from the Clinical Practice Research Datalink; a large, anonymised, UK primary care database. The sample included 262,844 patients who initiated antidepressant therapy between 1st January 2005 and 31st June 2011.
Results: 9.3% of patients switched to a different antidepressant product, with most switches (60%) occurring within eight weeks of the index date. The proportion switching was similar for SSRIs, TCAs and other antidepressants (9.3%, 9.8% and 9.2% respectively). Most switches were to an SSRI (64.5%), and this was the preferred option regardless of initial antidepressant class. Factors predictive of switching included male gender, younger (<18 years) and older age (>60 years), and history of self-harm and psychiatric illness.

Conclusion:
Over one in every eleven patients who initiates antidepressant therapy will switch medication, suggesting that initial antidepressant treatment has been unsatisfactory. Evidence to guide choice of second-line treatment for individual patients is currently limited. Additional research comparing different pharmacological and psychological second-line treatment strategies is required In order to inform guidelines, and improve patient outcomes.