Longitudinal patterns of antidepressant prescribing in primary care in theUK: comparison with treatment guidelines

The objective of this study was to determine whether patients beginning the rapy on the most common tricyclic antidepressants (TCAs) and selective sero tonin reuptake inhibitors (SSRIs) differed in their likelihood of having an tidepressant treatment that was consistent with recommended treatment guide lines in the UK. An analytical file constructed from a large general practi tioner medical records database (DIN-LINK) from the UK for the years 1992-9 7 was constructed. A total of 16 204 patients with a new episode of antidep ressant therapy who initiated therapy on one of the most often prescribed T CAs (amitriptyline, dothiepin, imipramine and lofepramine) or SSRIs (fluoxe tine, paroxetine and sertraline) were analysed. A dichotomous measure was d efined to indicate whether subjects were prescribed at least 120 days of an tidepressant therapy at an adequate average daily dose within the first 6 m onths after initiation of therapy. Only 6.0% of patients initiating therapy on aTCA and 32.9% of patients initiating therapy on a SSRI were prescribed antidepressant treatment that was consistent with treatment guidelines. Af ter controlling for observable characteristics, patients who initiated ther apy on a SSRI were much more likely (odds ratio = 7.473, p < 0.001) to have a prescribed average daily dose and duration consistent with recommended t reatment guidelines within the first 6 months of initiating therapy than we re patients who initiated therapy on a TCA. These findings suggest that ini tial antidepressant selection is an important determinant of whether the su bsequent course of treatment is consistent with current national guidelines for the treatment of depression in the UK.