Figure 7.

The preparation process and the mechanism of long-acting nanocrystals. This strategy is suitable for drugs/prodrugs with a low solubility in water. The manufacturing of nanocrystals can be achieved by milling or high-pressure homogenization. The long-term effect of the suspension of nanocrystalline is mainly achieved by the following two ways: (A) after im/sc administration, a primary depot of insoluble drugs/prodrugs can be formed in the site of injection, and then the drugs/prodrugs are slowly drained into the thoracic lymphatic vessels to form secondary depot. Subsequently, the active substance is gradually released from the lymphatic system into systemic circulation for long-acting effect; (B) after iv administration, macrophages phagocytize nanocrystals to act as a drug reservoir resulting in sustained drug release in systemic circulation. Reproduced with the permission from Ref. 116. Copyright © 2020 Elsevier.