“十八反”属于中药配伍禁忌，但在临床应用中出现过反药同方应用的情况。为揭示反药同方应用的理论基础，本文对古方中记载的反药同方进行分析，发现反药中存在归经相同、性味相反的药性组合，在反药同方应用中，常根据辨证取其中1 味药的非相反药性组合为主用，而相反药性组合相互制约，具有一定的保护作用。该规律有利于进一步深化反药的合理应用研究。

The "eighteen incompatible medicaments" is the incompatibilities in traditional Chinese medicine(TCM). However, in some special occasion, the incompatible medicaments can also be used in one prescription in the clinical applications. In order to reveal the theoretical basis for applications of incompatible medicaments in prescriptions, we analyzed ancient prescriptions and found that there are contrary Chinese herbal nature combinations (CHNCs) which have the same meridian tropism as well as the opposite nature and taste in prescriptions. In clinical applications, one of the non-contrary CHNCs was selected as the main response to syndrome differentiation. The contrary CHNCs in the same meridian tropism were used to restrict each other and therefore have the protective effects. The features found in this paper will be beneficial to further research on the rational application of incompatible medicaments.

国家自然科学基金委面上项目（30973946）：基于三阴三阳系统的药性组合模式及其作用机理研究，负责人：王耘；国家自然科学基金委面上项目（81173568）：基于三阴三阳的经方药对语法系统及其作用机制研究，负责人：王耘。