为协调一致，EMA与2012年10月18日发布指定单一立体异构晶型（对映体）、配合物、衍生物、或是不同盐或酯与相关的参照活性物质有关的新活性物质的考虑要点的意见书（Reflection paper on consideration given to designation of a single stereo isometric form (enantiomer), a complex, a derivative, or a different salt or ester as new active substance in relation to the relevant reference active substance）为判断参照活性物质的对映异构体、配合物、衍生物，不同盐或酯是否作为新的活性物质或存安全性或/和有效性在显著不同，及所需提交的注册资料提供说明。
相关法规要求及定义如下：
Article 10.2.b of Directive 2001/83/EC, as amended, states that the different salts, esters, ethers, isomers, mixture of isomers, complexes or derivatives of an active substance shall be considered to be the same active substance unless they differ significantly in properties with regard to safety and/or efficacy. In such cases additional information providing proof of the safety and/or efficacy of the various salts, esters or derivatives of an authorised active substance must be supplied by the applicant.
In addition according to the Notice to Applicant (Volume 2A, Chapter 1), a new chemical, biological or radiopharmaceutical active substance includes:
• an isomer, mixture of isomers, a complex or derivative or salt of a chemical substance previously authorised as a medicinal product in the European Union but differing in properties with regard to safety and efficacy from that chemical substance previously authorised.
