Background: The degradation of active pharmaceutical ingredients (APIs) and the subsequent formation of degradation products affect the pharmaceutical quality of a medicinal product. Therefore, quick and effective detection of adverse changes occurring in a medicinal product is very important. The aim of the present study was to assess the total directional hemispherical reflectance (THR) of effervescent tablets containing magnesium and vitamin B6 during storage at ambient conditions.

Methods: The expired (n=20; expiration date 04.2021) and unexpired (n=20; expiration 03.2024) tablets were analyzed. The measurements of THR were performed with the use of SOC-410 Directional Hemispherical Reflectometer (USA) within seven wavelength bands (from 335 nm to 2500 nm). For each tablet, 3 measurements were done. The study was funded within the project PCN-1-058/K/2/O.

Results: The mean THR was significantly higher within the ranges of 400-540 nm, 480-600, 590-720, and 1000-1700 for the unexpired effervescent tablets compared to expired tablets (p<0.001). In turn, a significantly higher value of THR for the range of 700-1100 nm, and 1700-2500 nm was observed for expired tablets than for unexpired tablets (p<0.001). Surprisingly, we have observed significant differences in mean THR between the top side and the bottom side of tablets.

Conclusions: The measurement of THR may be a rapid test for detecting adverse physicochemical changes in these tablets and can be used for a further detailed evaluation of API and related degradation products.