Trend in SSRI-SNRI antidepressants prescription over a 6-year period and predictors of poor adherence.

Purpose: To describe antidepressant (AD) use in the Emilia-Romagna Region (Italy) and to evaluate adherence to treatment with selective serotonin receptor inhibitors or selective noradrenaline receptor inhibitors (SSRI-SNRI).

Methods: Reimbursed prescriptions of AD were retrieved from the Emilia-Romagna Regional Health Authority Database. The overall AD consumption from the 2006-2011 period was expressed in terms of prevalence and amount of use. Adherence to treatment was assessed in a cohort of patients who received SSRI-SNRI, and was followed throughout a 6-month period from the start of each treatment episode. Adherence was considered according to three parameters: duration of treatment ≥ 120 days, prescription coverage ≥ 80 %, and gaps between prescriptions < 3 months. Determinants of non-adherent regimen, including sociodemographic and clinical variables, were identified by multivariate logistic regression by calculating adjusted Odds Ratio (adjOR) and the relevant 95 % confidence interval (95CI).

Results: From 2006 to 2011, the prevalence of use of AD increased by 5 % (from 86 to 90 per 1,000 inhabitants) and the amount of antidepressant consumption increased by 20 % (from 43 to 51 defined daily dose per thousand inhabitants per day [DDD/TID]), with a 14 % rise in the intensity of drug use (from 182 to 208 DDD per patient). Out of 347,615 SSRI-SNRI treatment episodes, only 23.8 % were adherent. Comorbidity (adjOR:0.69; 95CI:0.67-0.72) and recurrence of AD treatment in the previous year (0.91; 0.89-0.92) were associated with better adherence. Moreover, patients treated with duloxetine (0.58; 0.55-0.60), escitalopram (0.64; 0.62-0.66) or sertraline (0.65; 0.64-0.67) showed better adherence in comparison with paroxetine.

Conclusions: Clinical variables resulting in improved adherence seem to identify patients with more severe disorders and who actually need a pharmacological approach, whereas differences in adherence among ADs could in part be caused by channeling and sponsorship bias. Initiatives addressed at improving cooperation between primary care and psychiatrists could decrease AD prescription for cases of sub-threshold or mild depression that easily drop out because of rapid symptom relief or side effects.