Evaluating pharmaceutical reference pricing regulation in the EU: a hybrid resource/agent modelling approach

External reference pricing (ERP) regulation and its effect on drug access, affordability and availability in the EU has not previously been explored by dynamic simulation methods except through a single study using a discrete event simulation approach which paid limited attention to the adaptive behaviour of market actors.The authors have developed a hybrid agent based and system dynamics simulation model to explore the above mentioned effects of the ERP regulation including its impact on agents’ decision making. The building of the hybrid simulation model was supported by the use of Resource Agent Maps, a novel qualitative modelling technique designed to analyse the interactive behaviour of agents and resources in a complex adaptive systems environment. The development of the qualitative maps and quantitative simulation model ensured theoretical and methodological consistency and helped to support confidence in the simulation model building process. The simulation results demonstrate that the intended effect of the external reference pricing to decrease medicine prices results in the counter effect of maintaining higher prices for longer periods of time, market entry delays and withdrawal of medicinal products from the market.