The fundamentally different essence of two levels of information used in modern pharmacy, pharmacology and medicine for operations related to theoretical reasoning about medicines and the actual practice of their use in the treatment of specific patients is reported. In particular, the essence of theoretical information about medicines and norms of their use in accordance with the standards of medical care is analyzed. It is shown that the information about medicines and standards of medical care, dominating nowadays in textbooks, reference books, encyclopedias, scientific articles and normative and technical documents, is built on the idealized essence of chemically pure substances and idealized essence of their interaction with an idealized virtual patient. In this regard, in the fields of pharmacy, pharmacology, and chemistry, physics, and materials science, researchers to date have traditionally represented chemical elements (and drugs) by certain chemical formulas, names, and symbols for their molecules. Moreover, in pharmacy and pharmacology, the structural formula of one molecule of only one chemical substance belonging to the group of so-called main active substances most often plays this role. As a rule, this chemical symbol of its molecule is identified with the real substance itself. It is assumed that the substance in question is of ideal high quality, it is completely free of any impurities, it is not combined with other substances and does not represent a certain pharmaceutical product (it is not a tablet, not a solution, not an ointment, not an aerosol, etc.), and is not manufactured by a certain pharmaceutical company according to a certain recipe. At the same time, modern pharmaceutical products are not separate molecules, not pure chemical reagents, but all sorts of mixtures of different substances of different quality in different ratios. At the same time, each pharmaceutical product of each manufacturing plant and each series number has only inherent and unique mechanical, physical, chemical, physico-chemical properties and quality indicators. Therefore, the idealized essence of drugs is far from the essence of real pharmaceutical products. The chemical name and chemical formula are just a symbol of one molecule of a chemical element, reflecting its idealized chemical essence, but not the essence of a real "tablet", "ampoule" and/or "tube" with it. In turn, the virtual patient of average gender, average age, average health status, with a body weight of about 70 kg implied by the standards of medical care is just an idealized object of interaction with an idealized "medicine". In this regard, the study of the relationship between the idealized and real essence of drugs and patients is a crucial part of the problem of the relationship between theory and reality in pharmacy, pharmacology and in medicine.