Objectives <p>The Annual Price Revision (APR) based on external reference pricing (ERP) is one of the price control measures for the pharmaceutical sector implemented in Portugal. This study evaluates the impact of the APR on branded medicines in the outpatient market in Portugal between 2012 and 2023.</p> Methods <p>A retrospective longitudinal study with time series was conducted using national sell-out data for branded medicines from the outpatient market subject to the APR between 2012 and 2023. Data were retrieved from a panel of over 82% of community pharmacies and extrapolated to the national level. The impact was measured based on two outcomes: the annual and cumulative impacts, both analysed at current and constant prices. Both outcomes estimate the isolated effect of retail price variations resulting from changes in the maximum retail price. Additionally, the impact was assessed considering the inclusion of medicines in Homogeneous Groups (HGs) and according to payer segmentation.</p> Results <p>The annual impact ranged from a reduction from 128.4 million euros in 2012 to an increase of 2.7 million euros in 2023<b>.</b> Overall, the value of the total cumulative impact of the APR between 2012 and 2023 amounted to 5.3 billion euros. The impact was greater in patent-protected originator medicines, reaching 81.7% in 2023. The public entities captured 56.9% of the total price reductions.</p> Conclusions <p>This study provides a valuable contribution to the evaluation of price regulation measures based on ERP and can support decision-making by helping to identify and select specific criteria for future price revisions.</p> JEL classification <p>I; I1; I11; I18; I19</p>