Monitoring of recrystallisation of microcrystalline cellulose inside pharmaceutical tablets during storage using near infrared diffuse reflectance spectroscopy

摘要

Changes in the crystallinity of microcrystalline cellulose (MCC) inside pharmaceutical tablets during storage were monitored by near infrared (NIR) diffuse reflectance spectroscopy to investigate transient variation at the molecular level. The MCC used in the tablets was ground before tablet formulation to intentionally cause a decrease in crystallinity. The variation in crystalline structure of MCC was evaluated from the intensity of NIR spectra peaks ascribed to OH groups in the crystalline region. The MCC exhibited clear signs of recrystallisation during 63 days of storage. In addition, the recrystallisation became even more pronounced when the MCC was stored under high-humidity conditions. Results also showed that the inclusion of anhydrous silicic acid induces a clear delay in recrystallisation by restricting the penetration of water molecules into the tablets. The findings derived from NIR spectra were substantiated by differential thermal analysis. The results from this study suggest that crystallinity of MCC inside tablets can be controlled by other excipients during storage, which has useful applications for controlling pharmaceutical product performance during storage.