ABSTRACT
″Herb-Pairs″, also known as pair drugs, refers to a prescription consisted of two relatively fixed traditional Chinese medicine, is the most basic, most simple and most common form of medication prescription in traditional Chinese medicine compound compatibility. It is not a random combination of two herbs, nor is the simple accumulation of efficacy, but the simple and delicate experience of ancient Chinese medicine practitioners. As a bridge between single drug and prescriptions, it is the embodiment of the regular and dialectical connotation. Therefore, research on Herb-Pairs has always been the most basic and most important entry point for compound compatibility studies. However, the interaction between herbs and herbs is an effect with a downside as well as benefits. The beneficial herb-herb interaction in Herb-Pairs include mutual promotion, mutual enhancement, mutual restraint between two drugs and counteract toxicity of another drug. And the harmful herb- herb interaction in Herb- Pairs includes mutual inhibition and antagonism. All of these interactions areby means of affecting the metabolism of components to play a therapeutic effect. Using the pharmacokinetic-pharmacodynamic (PK-PD) binding model, the combination of drug metabolism and pharmacodynamics can further elucidate the influence on effect caused by drug concentration and metabolism, which can help elucidate the mechanism of drug action. Consequently, in this review, the herb-herb interactions in terms of pharmacokinetic were summarized to elucidate rule of TCM compatibility.