Comparative Effectiveness of Generics and Brand-name Venlafaxine On Costs and Outcomes in the Real World Medical Care of Patients with Generalized Anxiety Disorder

Aim : To determine patient adherence to generic venlafaxine versus brand-name venlafaxin (Vandral®) and its impact on costs and outcomes in subjects with Generalized Anxiety Disorder (GAD) in routine medical practice in Spain. Methods : A retrospective, observational new-user cohort study was designed. Electronic medical records linked from medical database of BSA, a health provider in Badalona (Spain), and corresponding community pharmacies dispensing's were extracted for analysis. Participants were beneficiaries aged 18+ years with pharmacy dispensing drug coverage between 2008 and 2012, an ICD-9-CM code for GAD and who initiated treatment with generic-venlafaxine or Vandral®. Assessments included adherence (measured as the medication possession ratio [MPR] and time until discontinuation up to 1 year follow-up), healthcare costs funded by NHS and outcomes (measured as the reduction in severity of anxiety symptoms with the HAM-A scale). Differences were estimated using a general linear model with covariates. Results : A total of 841 patients (60.7 years, 64% women) were identified: brand-name; 370 (44%) and generic; 471 (56%). The average MPR was 78% in the generic arm and 82% in the brand-name (p=0.047). Median persistence was 8.1 and 8.8 months, respectively (p=0.002). A 16% reduction in the adjusted healthcare cost was observed favoring brand-name; €1,110 vs. €928€; -€182 (p=0.020). Brand-name was associated with higher reduction in symptoms severity: -15.3 (62%) vs. -12.6 (49%) points (p<0.001).
Conclusions : Compared with initiating generic-venlafaxine, patients initiating brand-name venlafaxine were more likely to adhere, had lower NHS funded healthcare costs and showed higher reduction of anxiety severity symptoms in routine clinical practice.