What issue in tableting is characterized by an unequal distribution of color?

The issue characterized by an unequal distribution of color in tablets is referred to as mottling. This occurs when the active pharmaceutical ingredient or the excipients are not evenly distributed within the tablet formulation, resulting in areas of varying color intensity on the tablet surface. Factors that contribute to mottling include the method of blending powders, the moisture content of the excipients, and differences in particle size or color of the materials used in the formulation.

Mottling can be problematic as it affects the aesthetic appearance of the tablets and may lead to inconsistencies in dosage if the color is indicative of the concentration of the active ingredient. Addressing this issue typically involves optimizing the mixing process, using colorants uniformly, and ensuring the proper flow characteristics of the powders during tablet formation.