有一些药物如某些维生素、激素、抗菌素、抗毒素、强心甙等,不能根据其理化性质检定质量规格时,往往采用生物实验方法并与标准品加以比较来检定其效价。通过这种生物检定,具有一定生物效能的最小效价单元就叫做“单位”(U.);经由国际协商规定出的标准单位,称为“国际单位”(IU.)。一个单位或一个国际单位,可以有其相应的重量,但有时也较难确定。单位与重量的折算在不同的药物是各不相同的。 Some drugs such as certain vitamins, hormones, antibiotics, anti-toxins, cardiac glycosides, etc., can not be based on the physical and chemical properties of the test quality specifications, often using biological experiments and compared with the standard to test its potency. The minimum titer unit with a certain bioeffect through this bioassay is called the “unit” (U.); the standard unit stipulated through international negotiations is called the “International Unit” (IU.). A unit or an international unit can have its own weight, but sometimes it is more difficult to determine. Unit and weight of the conversion in different drugs are different.