The impact of regional physician association regulations on the biosimilar prescription behaviour in Germany

The Impact of Regional Physician Association Regulations on the Biosimilar Prescription Behaviour in Germany

Benjamin Birkner¹ (with Friederike Arndt² and Katharina Blankart³)

1 University of Hamburg, HCHE

2 University of Duisburg-Essen, CINCH

3 University of Duisburg-Essen, CINCH, Leibinz Science Campus Ruhr


Biosimilars are a less costly alternative to original biological drugs. Although only four percent of the insured receive biologics, they are responsible for 21 percent of drug expenditure. In addition, the proportion of biosimilar prescriptions in Germany varies greatly between regions. The aim of this analysis is to investigate the influence of the introduction of regulations (quotas, prioritized prescribing) by physician associations (PAs) on the prescribing behavior of physicians in Germany.


Our data consists of the drug agreements (Arzneimittelvereinbarungen) of the PAs and data sets of national outpatient services and prescription data for the period 2009-2015. We focus on the active substances somatropin, erythropoiesis stimulating agents (ESA) and filgrastim. Using a lagged-dependent variable approach, the prescribing behavior of physicians in PAs with regulation is compared with that of physicians in PAs without regulation. Outcome variables are the proportion of biosimilar prescriptions and the number of prescriptions of biologics and biosimilars. We control for regional differences as well as practice and patient characteristics.


On the one hand, we find positive effects for the frequently prescribed active substances ESA and filgrastim. On the other hand, physicians did not react to regulations for somatropin. Where significant effects were identified, the introduction of regulations increased the proportion of biosimilar prescriptions on average between 2.7 and 14 percentage points (p<0.01). Overall, a regionally heterogeneous picture emerges. For example, the number of prescriptions of original drugs decreases due to the introduction of the priority prescription in the PA Bremen, while opposite effects can be observed for the introduction of a quota in other PAs.


The effect of regulation on the prescribing behavior for biosimilars is not uniform. There were no clear effects of regulation depending on the introduction of explicit quotas or priority prescription requirements. Due to unobservable factors such as price reactions by manufacturers and individual discount agreements of insurers, it is not possible to determine the causal effect of the measures conclusively yet.