Biological drug is a drug containing one or more active substances produced or secreted from a biological source. Some of them may be previously present in the human body, and examples include proteins such as insulin, growth hormone or erythropoetin. Biosimilar drug is a medical product that is a copy of the original approved drug whose patent has expired. Strict rules apply to similar biological medicines: 1) it is unable to support extrapolation of data on safety and efficacy between individual indications, except in the case of appropriate, science-based evidence; 2) biosimilar drugs must meet the requirements associated with testing the immunogenicity and safety monitoring afterthe introduction of the drug in clinical practice, including the risk management program; 3) each biosimilar drug has to be labeled under its own name in order to allow clear traceability of all medications; and 4) the principle of automatic substitution cannot apply to biosimilar drugs because they are not interchangeable.