Some drugs have poor compressibility and flowability, and should be improved by using a dry granulation mechanism. However, these drugs are sensitive to moisture and heat, and are not stable enough. Therefore, dry granulation can be used to compress the tablets. Namely: After mixing the drug powder and necessary excipients evenly, use appropriate equipment to press it into a solid (block, sheet or particle), then crush it into dry particles of appropriate size, and finally press it into tablets. Usually, a hydraulic press is used to press the mixture of drugs and excipients into thin solid sheets, or a specially designed tablet press with high pressure can be used to first press into large tablets (also known as the "tablet press method"), and then crush them into small particles before pressing them into tablets.

Dry granulation machineDirect compression of powder into tablets

There are special requirements for excipients, as the vast majority of drug powders do not have good compressibility and flowability, and excipients need to be added to compensate for these deficiencies. Therefore, it is required that the auxiliary materials used have good compressibility and flowability, and can still maintain this good performance after mixing with a certain amount of drugs. There are many pharmaceutical excipients used for direct powder compression abroad, such as various types of microcrystalline cellulose, spray dried lactose, dicalcium phosphate dihydrate, compressible starch, micropowder silica gel (excellent flow aid), etc.