On 2009, at the Neurological Institute of Havana, Cuba, was conducted a double-blind, placebo-controlled study of 225 patients with clinical definite relapsing remitting (RR) MS and brain MRI confirmed. Patients were randomly assigned to receive intramuscular Interferon (IFN) alpha-2b (Heberón alfa R) 20 million IU (high dose), 6 million IU (low dose) or placebo weekly for 2 years.