Active Pharmaceutical Ingredients (API), popularly  speaking, are the raw materials of medicines, only pharmaceutical raw materials are processed into pharmaceutical preparations , can they become medicines available for clinical use, so drugs we usually eat  are  the finished drugs  through processing.

Active Pharmaceutical Ingredients based on its sources can be divided into two major categories ,including  chemical synthetic drugs and natural chemical drugs.

Chemical  synthetic drugs can be divided into organic synthetic drugs and inorganic  synthetic drugs. Inorganic synthetic drugs are inorganic compounds (  very few is element), such as aluminum hydroxide, magnesium trisilicate which are used for the treatment of gastric and duodenal ulcers ; organic synthetic drugs are mainly composed of  drugs made by  basic organic chemical raw materials, through a series of organic chemical reactions  (such as aspirin, chloramphenicol, caffeine, etc.).

Natural chemical drugs ,based on its sources,can be divided into two categories including biochemical drugs and plant chemical drugs. Antibiotics are generally made by the microbial fermentation,  which belongs to the biochemistry category. A variety of semi-synthetic antibiotics occurs in recent years,which are biosynthesis and chemical synthesis combining products.Among active Pharmaceutical Ingredients, the organic synthetic drugs varieties, yields and values have  the largest proportion,which are  the main pillars of the chemical and pharmaceutical industries. The quality of active Pharmaceutical Ingredients  decides whether the formulation is good or bad , so its quality standards are very strict  ,countries in the world have developed national pharmacopoeia standards and strict quality control methods for its widely used active Pharmaceutical ingredients.