The Impact of UV Radiation on the Hemispherical Reflectance Values and Homogeneity of Tablets Containing Clindamycin and Phenoxymethylpenicillin

Background: The pharmaceutical industry is faced with the problem of how to design and conduct tests to assess photostability during drug use and storage. In this study, the aim was to analyze the changes in total hemispherical reflectance (THR) and homogeneity in two preparations of tablets with clindamycin or tablets with phenoxymethylpenicillin stored under UV radiation. Methods: The analysis was performed for coated tablets with two types of antibiotics in and out of the direct package (i.e., non-blister and blister). The condition of UV radiation was maintained over 7 days in a Solarbox 1500 chamber. THR values were assessed after 3 and 7 days using a SOC-410 reflectometer. Hyperspectral evaluation was carried out with Specim IQ hyperspectral camera every 3 nm from 400 nm to 1030 nm. Results: THR values for both blister and non-blister tablets with clindamycin decreased significantly for the ranges 400–540 nm, 480–600 nm, 590–720 nm, and 700–1100 nm on day 3 of UV exposure. For non-blister clindamycin tablets, THR increased slightly on day 7 of the experiment compared to day 3, while THR continued to decrease for blister tablets. THR values for non-blister phenoxymethylpenicillin tablets decreased slightly on day 3 of UV exposure for the ranges 400–540 nm, 480–600 nm, 590–720 nm, 700–1100 nm, and 1000–1700 nm, and then on day 7 of UV exposure THR values increased to near baseline. In addition, non-blister clindamycin tablets showed a tendency to increase in a difference between max–min reflectance in the total spectral range as well as in visible and infrared light (p < 0.001 each). Similarly, day 7 blister tablets with clindamycin had a significantly higher max–min reflectance difference compared to day 3 blister tablets but only in the range of visible light (p = 0.034). Thus, the lowest homogeneity was demonstrated for 7 day tablets. On the contrary, the lowest homogeneity was observed for phenoxymethylpenicillin tablets on day 0 of experiment. Conclusions: UV radiation affects the total hemispherical reflectance values for clindamycin and phenoxymethylpenicillin tablets, but to a different extent and within a different spectral range for each type of tablet. The homogeneity of the tablets may also change over time with UV exposure.