OBJECTIVES:  To reduce the increase of the expenditure in disease-modifying drugs (DMD) used in the first line treatment of remitting-relapsing multiple sclerosis (RRMS) by forcing a decrease in the price of drugs, as a consequence of the introduction of competition mechanisms. METHODS: By the second half of 2009,  the first biosimilar drug of beta-interferon (bIFN)-1b Betaferon® (Extavia®), gained access to the Spanish market, and as a consequence of the acquisition public contest set up by our hospital, Extavia® was selected, with 7% discount. At that time, bIFN-1b was used in about 40% of RRMS patients treated in first line. By the end of 2010, the Pharmacy  Comitee evaluated the different DMD, taking as starting an Andalussian Agency for Health Technology Assessment report, and stated that bIFN-1a sc (44 mg), bIFN-1b and Glatiramer acetate were therateutic equivalents for the initial treatment of RRMS. An open contest was announced to select the drug to be used as first line treatment. The lowest therapeutic equivalent daily treatment cost was selection criterion. All new patients were commenced on the drug selected. A comitee composed by the Medical Manager and the heads of the Neurology and the Pharmacy departments assesses the requests for treatment in each case.  The cost difference between the selected treatment and average cost before the evaluation  was multiplied by the total number of new  patients  to calculate savings generated. RESULTS: Overall, cost per patient was reduced by 4.5% when Extavia® was selected as bIFN-1b. When, in a second step, bIFN-1b was designated as first line drug for RRMS, cost per  patient decreased by an additional 7%.  A total of 150,000 € (one year)  was saved as a result of this strategy.  CONCLUSIONS: Therapeutic equivalence offers a sound means to improve the efficiency beyond that obtained with biosimilar drugs, especially in high cost drugs used in chronic illnesses