Generic drugs play an important role in healthcare systems as they represent an effective and more affordable alternative for the population. In Peru, a regulation of interchangeability of generic drugs (also called multisource drugs) was stablished to define the procedures and requirements for developing in vivo and in vitro therapeutic equivalence studies, following the gradual application approach and sanitary risk criteria. Compliance with the new regulation will allow greater access to effective, safe and quality generic drugs. Meanwhile, drugs continue to be marketed in the absence of therapeutic equivalence stu-dies. Findings show that some drugs failed in in vivo and in vitro comparisons with the reference product. This regulation represents a great challenge for manufacturers and holders of sanitary registrations in order to demonstrate the interchangeability of their pharmaceutical products with the reference product.