This article aims to study the relationship between availability, prices of medicines and public health interests. We have used an analysis methodology of the economic interests involved and a systematic method of treatment of national, international, community and Andean current legislation. Also we have relied on comparative law methodologies between our domestic law and the ones of other countries in the Western World. There is a close link between the availability and prices of medicines and public health interests. Our current legal system recognizes to the inventors of new medicines as a monopoly to negotiate in the pharmaceutical market. To protect public interests, our regulation establishes some limits to the rights of inventors. Property rights are limited in time and under some circumstances it is mandatory to authorize others to use the patent under a licensing agreement. The World Trade Organization (WTO) has established (Decision of the Council of the WTO Doha Round, 2003.) other limits to these rights in case of exceptional conditions. Our Constitution gives prevalence to public interests over private ones. It is the duty of governments to establish a fair system in which inventors can obtain a financial reward for their creations and society can satisfy its health needs.