Hydrolysis reaction: Gelatin capsules are easily hydrolyzed below pH ph and above pH 10. The viscosity of the mixture after hydrolysis increases and the dissolution rate becomes slower.
Temperature, humidity, light: Protein denatures under high temperature conditions. The highly hygroscopic content can delay the disintegration of the gelatin capsule shell after it loses water. The reason is that the gelatin fiber crosslinks after moisture absorption, the hydrogen bond is not easily broken when it is dissolved. Intense ultraviolet and visible light exposure can cause gelatin changes. Therefore, under high humidity and long-term illumination conditions, the disintegration characteristics of the capsule will change, thereby prolonging the dissolution time.
Aldehyde cross-linking: lysine and aldehyde in gelatin are subjected to multi-step crosslinking under moist heat conditions. The cross-linking reaction causes gelatin to form larger molecules and a tighter network structure, preventing drug release, resulting in delayed disintegration of the capsule.
Reduction reaction: The highly reductive content reacts with gelatin in Maillard. This reaction causes a change in the performance of the capsule, causing abnormal dissolution of the capsule.
Excipient influence: talc powder can properly prevent gelatin hydrolysate from accumulating with each other, resulting in slower dissolution of capsule shell. The surfactant can appropriately accelerate the dissolution rate of the gelatin hydrolyzate.