The effect of the acid-base chemistry of lactose on its adhesion to gelatin capsules: Conclusions from contact angle measurements and other surface chemical techniques

摘要

Dry powder inhalation formulations are used for drug delivery to the lungs. Lot to Lot variations in respirable dose limits the success of such formulations in the marketplace. The present authors offer the hypothesis that the performance of dry powder inhalation formulations depends upon the adhesion strength between each component of the formulation. Here we explore the adhesion of lactose to gelatin capsule materials found in dry powder inhalers. The surface characterization of each of these materials has been performed using a variety of techniques. Some of the experimental techniques used include contact angles, IGC, FMC, and XPS (ESCA) as well as SPM. Each of the pharmaceutical grade materials used in the study was found to have varying degrees of surface contamination which, in turn, affects the adhesion strength between these materials. From our experimental data it is clear that acid-base interactions contribute significantly to the adhesion between these materials and that such interactions are to a significant degree responsible for inter-lot performance variation. Reduction in the acid-base character of either or both lactose particles and capsules materials can reduce inter-lot variation in product performance.