What principle is used to design the osmotic controlled release system of water-soluble drugs so as to achieve the purpose of sustained release?

Composition, materials, semipermeable membrane materials, penetration enhancers, propellants and release holes of osmotic pumps.

Controlled release principle: it uses osmotic pressure principle to control the release of substances. The tablet core is made of water-soluble polymer or other auxiliary materials, and the outer surface is coated with water-insoluble polymer (such as cellulose acetate, ethyl cellulose or ethylene-vinyl acetate polymer). ) to form a semipermeable membrane shell. Water can penetrate into this film, but water can't. Then, laser is used to open one or more release holes in the coating film. When in contact with water, water enters the tablet core through the semi-permeable membrane, so that the substance is dissolved into saturated solution or suspension, and with the dissolution of auxiliary materials with high osmotic pressure, a hypertonic solution is formed in the tablet membrane. Due to the large osmotic pressure difference between the inside and outside of the membrane, the substance is continuously pumped out through the release hole, and its outflow is equal to the amount of water infiltrated into the membrane until the substance in the nucleus is completely dissolved.