Impact on In- and Out-of-Hospital Drug Prescriptions of Including a More Expensive Me-Too Antidepressant in a Hospital Drug Formulary: a Controlled Longitudinal Study

Abstract

Background: The effect of the inclusion of a more expensive me-too medicine in a hospital drug formulary (HDF) on both in- and out-of-hospital utilization, and the contextual factors which influence this type of induction is rarely studied. Accordingly, this work aimed to quantify the effect of the decision of a hospital of including a more expensive me-too antidepressant in its HDF. Methods: A controlled longitudinal study was carried out in a Regional Health Service of Spain. We performed a segmented regression analysis with control group. We used the following dependent variables: defined daily doses (DDD) per 1000 inhabitants per day, DDD per 100 bed days, and cost per DDD. Results: At a hospital level, the modification in the formulary led to utilization changes: (1) an increase in immediate consumption of the newly included me-too drug; and, (2) an annual 25.96% [95% CI: 2.96%–48.95%] decrease in the adjusted trend of the already existing parent antidepressant. The adjusted trend of the cost per DDD of the sum of all medications in the therapeutic group increased by 20.03% annually [95% CI: 3.24%–36.82%]. In the out-of-hospital setting utilization changes were: (1) the adjusted trend of the newly included me-too drug rose by 12.14% annually [95% CI: 4.97%–19.30%]; and, (2) that of the parent drug underwent a negative change in trend of 4.18% annually [95% CI: 0.00%–8.36%]. Conclusions: The inclusion of a more expensive me-too drug in the HDF led to increased consumption of this more expensive me-too drug both in- and out-of-hospital.