Someone tried to improve the bioavailability and dissolution rate by preparing crystalline particles of 638.7nm-814.8nm. Under the premise of sodium lauryl sulfate as a stabilizer, anti-solvent precipitation technology is used. For this purpose, four different PVPK30 concentrations of 0.05, 0.1, 0.2 and 0.4% were prepared. All the formulations are in the grade range. Compared with the micron grade, the dispersing and dissolving ability of the medicine has been significantly improved. When the concentration of PVPK30 was set to 0.4%, the drug showed a higher dissolution rate of 70%. The unpolished micron grade only shows 10% for the same time. 3.2 Crystals in the form of crystals refer to crystals whose average diameter is less than 1000 nm. Common methods for preparing crystals include precipitation, high-pressure homogenization, wet milling and spray drying. In some dosage forms, the saturated solubility of the crystals increases, which helps to diffuse in the skin.

Crystals are different from particles composed of a matrix and a combination of particles. In other words, they are composed of crystalline forms in a range of sizes. In recent years, crystals have rapidly developed into a promising drug delivery strategy. At present, crystals of sirolimus, aprepitant, fenofibrate, megestrol acetate, paliperidone, and palmitate have been prepared and entered the market. Sirolimus crystals were launched as a marketed product in 2000 and are available in oral liquid and tablet forms. Compared with the solution, the bioavailability of rapamycin tablets is increased by 21%-27%. A single oral dose of rapamycin is 1 or 2 mg, and the total tablet weight is about 365 mg to contain 1 mg of the main ingredient. This means that the weight of the crystal form in the tablet is very small. Aprepitant crystal capsules, containing crystal spheres, are two listed products launched in 2001. This single dose of 80 or 125 mg can treat vomiting. TriCor? tablets containing fenofibrate crystals and Megestrol Acetate ES?, which is used to treat HIV-related anorexia, are the next three and the fourth on the market, respectively. 

Nifedipine has poor water solubility, with a solubility of 20μg/ml. Due to its poor solubility, its dissolution and bioavailability are low. Compared to unmilled commercial NIF products, the NIF crystals prepared by Hecq and his colleagues showed a higher dissolution rate. They use high-pressure homogenization to reduce the particle size. According to the author's description, this method is considered to be a simple and effective way to reduce the particle size, and it has strong applicability for drug hardness and stabilizer types. Grade drug crystals can dissolve 95% at 60 minutes, while the unground drug only has 5%.