By example of abacavir sulfate – a parent drug substance protected by a series of patents – it is demonstrated that neglect of the physicochemical properties and chemical laws, together with incorrect use of terminology, allowed additional patent protection for this drug to be carried out. In Eurasian patent EA 001809, the correct name of original substance was replaced by incorrect synonym and some contradictory, not quite reliable data, together with data presenting no novelty about the object were introduced into the formula of invention. This approach to prolongation of the period of patent protection for the parent drug substance is impermissible scientifically and inacceptable ethically. The results of investigation of abacavir sulfate by the method of x-ray diffraction (USP RS) showed that this substance is completely identical to abacavir hemisulfate according to published data on the crystalline structure of this drug. Indeed, both substances are neutral salts, have the same molecular formula (C 14 H 19 N 6 O) 2 SO 4 , and possess a molecular mass of 670.76. Therefore, there were no grounds to repeatedly patent the existing drug (abacavir sulfate) under the name of abacavir hemisulfate, which is erroneous for the neutral salt (1 S ,4 R )-4-[2-amino-6-(cyclopropylamino)-9 H -purin-9-yl]cyclopent-2-en-1-methanol.