Terahertz imaging of titanium dioxide-free film coating hydration and tablet core interactions

Titanium dioxide (TiO₂) is often used as a white base pigment in film coatings, but recent EU restrictions on its use in food have prompted pharmaceutical manufacturers to seek alternatives. Terahertz pulsed imaging (TPI) was used to examine the hydration of TiO₂-free immediate release formulations, either without an opacifier or using calcium carbonate (CaCO₃). The coatings, made from polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose (HPMC), were approximately 100µm thick. TPI results indicated that the type of film coating influenced hydration and scattering effects. However, there was no evidence that TiO₂-free coatings compromised tablet disintegration. Although the HPMC coating with CaCO₃ gelled upon hydration, the tablets fully hydrated within the required time. These findings offer insights into the mechanistic impacts of alternative coatings in the industry.