Effect of Moisture Sorption and Lactose Type on Tablet Quality: A Hygroscopicity Study between Lactose Powder and Tablets

Lactose is one of the most commonly used tablet diluents and fillers. However, the moisture sorption of lactose powder could exert detrimental effects on the excipient itself, as well as on the tablet quality. The effects of storage relative humidity (RH) conditions for different grades of lactose powders and tablets on compression behavior and tablet qualities were investigated. Four types of lactose were selected in this study: sieved lactose (Pharmatose 110M), granulated lactose (SuperTab 30GR), anhydrous lactose (SuperTab 21AN), and spray-dried lactose (SuperTab 14SD). These powders and tablets were stored at three RH levels (33, 58, 75%) for a certain period of time before determining their properties. For the moisture-sorbed powder, there was little change in the basic physical properties of lactose powder. Based on the dynamic vapor sorption (DVS) results, the lactose grades determined their hygroscopic properties. The reduction in mechanical strength of lactose powder during storage became less pronounced except for 14SD. But a reduction was observed in the tensile strength (TS) of the 14SD powder from 2.1 to 0.9 MPa after storage at 75% RH for 30 days. The fragmentation of lactose increased with increasing storage humidity. By using multivariate statistical analysis, the similarity and variation of powder properties between 14SD and other types of lactose were visualized. For the moisture-sorbed tablet, the TS became higher and the friability became lower. The TS of lactose tablets exhibited an increase of up to 59.8%. Whether water uptake occurred before or after compression adversely affected tablet disintegration. In conclusion, adverse phenomena during production and storage can be effectively minimized by a better understanding of the effects of moisture sorption on lactose powder and tablets.