OBJECTIVES: Tight public budget constraints have accelerated the debate on the extent of prescribed medications that are publicly covered in Spain, a country with one of the lowest percentage of OTC sales over total drugs sales. The objective of this study is to examine the economic impact of payer policies consisting on a hypothetical Rx-to-OTC switch of 5% of currently publicly covered prescription drugs for mildest conditions. METHODS: A decision model is used to estimate the economic impact of the switch. Both third-party-payer and societal perspectives are adopted, using a five-year timeframe, both at regional (17 regions) and national levels. The model is inspired by a previous ones in European countries, but the timeframe and the effects measured have been further developed for the sake of robustness and better reflection of the current Spanish reality. The effects, measured in monetary units, include those regarding to quality of primary care, labor productivity, the opportunity cost for non-working populations, and financial burden of pharmaceutical expenditure. Resources allocated to improving responsible self medication are also accounted for. The study analyses the effects on different stakeholders (patients, NHS, and society). Finally, it includes both a standard and a probabilistic sensitivity analysis. RESULTS: The switch results in a 3.125€ millon societal effect, explained by improving quality of primary health care (2.258M€), improving labor productivity (507), optimization of non working patients’time (579) and a reduction of public expenditure on publicly covered medication (979). On the other hand, there are negative effects from increasing privately funded drugs (1.165) and the cost of improving self-care (35). Sensitivity analyses confirm overall results (p<0,01). CONCLUSIONS: Under increasing budgets constraints, switching drugs for mild conditions may be a solution with positive societal net effects, although the distribution of the impacts among stakeholders might make the initiative unpopular.