Development of Tablet Coloration Evaluation Method using Color Difference Values

During quality control audits for dispensed medications, tablet coloration is frequently checked along with the subjectivity of pharmacists in pharmacies. This study developed an objective method for evaluating tablet coloration using color difference values derived by analyzing tablet images. We took photographs of the test tablets and imported these images into ImageJ to obtain the RGB (red, green, blue) color code chart values. Next, the RGB values were used in the CIE2000 calculator to calculate the color difference between each reference tablet that was immediately removed from packaging. We induced color changes in telmisartan (TEL) tablets of 19 products as test tablets by contacting them with the levodopa–carbidopa (LEV) tablet, and the color difference values for these tablets were calculated. Subsequently, the same tablets were evaluated by 10 clinically experienced pharmacists, auditing the acceptance of the coloring of these tablets. The receiver operating characteristic curve analysis between the color difference values and acceptable evaluation by pharmacists indicated a cutoff color difference value of 2.08, with an area under the curve of 0.756 as acceptable. After storing TEL tablets in one-dose packaging with LEV tablets for 1 month at room temperature in care facilities, 36％ of the tablets showed color difference values exceeding the cutoff threshold. Using color difference values in objective tablet coloration evaluation suggests its applicability in assessing tablet coloration in clinical settings.