Hemispherical Directional Reflectance as a Screening Tool to Distinguish Effervescent Tablets with Acetylsalicylic Acid and Vitamin C Stored Under Stress Conditions from Those Stored in Ambient Conditions

Since exposure to light may adversely affect drug effectiveness and safety, quality control of a pharmaceutical preparation includes assessing its sensitivity to light. The present study aimed to examine the photostability of effervescent tablets containing acetylsalicylic acid (ASA) and vitamin C, exposed to heat and UV rays, using a portable device emitting radiation in a wide spectral range from UV through visible light to near-infrared. Effervescent tablets from the commercial formulation (expiration date July 2025) were tested in the study. For each tablet, the value of total hemispherical reflectance (THR) was evaluated during the application of stressful conditions, i.e. different temperatures (22 ℃, 30 ℃, and 45 ℃) and simultaneous UV radiation. The THR was measured using a hemispherical reflectometer (SOC410, USA) at the beginning and at the end of the experiment (day 0 and day 7, respectively). Control tablets (day 0) showed significantly higher mean THR values in all spectral ranges except for the 1000–1700 nm range while the lowest average THR values were demonstrated in the ranges of 335–380 nm and 1700–2500 nm for tablets after 7 days at 30 ℃ and UV radiation. For the ranges of 335–380 nm, 400–540 nm, and 480–600 nm, the THR values decreased for tablets stored at higher temperatures and under UV light compared to the control tablets. The study proved that after exposing effervescent tablets to heat and UV radiation, the THR decreases, which may result from some physicochemical changes that have occurred during storage.