ABSTRACT

The SPM results show that gelatin capsule 29625, which exhibits high-contrast friction, tends to have high adhesion, whereas gelatin capsules 72601 and 29625ext, which exhibit low-contrast friction, have low adhesion. The surfaces of capsules 72601 and 29625ext also appear to be of relatively uniform friction, which is in accordance with the observed relatively constant adhesion. On the other hand, the nonuniform friction associated with capsule 29625 correlates with the observed spatial variation in adhesion. The implication is that the physicochemical nature of the capsule surface, which is dependent on the gelatin and mold release agent used in the capsule manufacturing process, is a crucial factor in the adhesion of lactose particles to gelatin capsule surfaces. Further systematic investigations are underway in our laboratory to provide a more complete basic understanding of the adhesion of pharmaceutical particles in dry powder inhalation products.