OBJECTIVES: To analyze how main determinants of competition in six therapeutic target groups -analgesics, tranquilizers, peptic ulcer treatment, cholesterol treatment, benign prostatic hypertrophy and ACE inhibitors- were affected by regulations and drug policies implemented at national level during the last decade in the pharmaceutical market in Argentina. METHODS: The database corresponds to the annual information on retail sales in the Argentine pharmaceutical sector generated by IMS for the period 2005-2012. The estimation strategy takes the form of econometric models of ordinary least squares with year fixed effects and robust standard errors. The dependent variables explain the market shares of each product/brand per therapeutic class, explained by prices, participant active principles, and a set of variables capturing product differentiation mechanisms implemented by pharmaceutical firms. Each therapeutic class’ regression was exposed to a vector of variables capturing the structure of the regulatory framework. RESULTS: In general, prices do not show to be significant determinants of market shares, unlike factors associated with mechanisms of product differentiation do, proving they facilitate the development of brand loyalty and adherence, even with relatively higher prices. On the other hand, the inclusion of new active principles in the Compulsory Health Program (CHP) will act as a boost for priority prescriptions, while the production of generic medicines increases competition, reducing market shares. In addition, the impact of these policies rests heavily on the structure of competition in each therapeutic class. CONCLUSIONS: The main health policy recommendations suggest: the need to develop new areas of collaboration with the pharmaceutical sector, enhancing competition in markets with higher levels of concentration, facilitating the evaluation of policies on generic medicines, and successfully regularizing the structure of drugs and products available through the CHP.