OBJECTIVES: In order to improve the medication access for the Brazilian citizens, the CAP (Price Coefficient), which is the mandatory minimum discount, was regularized by the Brazilian Chamber of Pharmaceutical Market Regulation in December 2006. This discount must be used not only on the prices of high cost drugs, when they are purchased by the government, but also on every medication which are obtained by judicial process. The objective of this study is to present a case study which evaluates the fulfillment of CAP on the acquisition by judicial process of a medication indicated to treat a rare disease. METHODS: Economic information (number of units sold and total sales from governmental acquirements per month, number of patients treated by the new drug) between December 2010 and November 2012 were provided by the pharmaceutical industry from two different via. One of them is the mandatory annual report of commercialization, which is an instrument to monitor the Brazilian pharmaceutical market. The other information source is the requirement, which was made when the entry price was established for that specific technology. RESULTS: During the period of the study, all the medications were bought through the judicial process by the SUS (Brazilian Public Health System) and the CAP was properly used; the sale price practiced was much close to the maximum government sale price. However, there are differences between the information: the number of patients, the number of units sold and the total sales. CONCLUSIONS: Especially in cases of medications with high treatment cost, it is very important to assess the use of the CAP discount by different way of requirement, not only by the annual commercialization report. The CAP discount allowed improving the medication access by SUS with lowest price, more than 20% of the discount on the maximum fabric price.