Film coating density and thickness: Critical quality attributes for immediate release tablet disintegration control

While designed for rapid drug release, immediate release (IR) film coatings can transiently impede water transport, affecting tablet hydration. The impact of coating density and thickness on hydration kinetics was investigated using polyvinyl-alcohol-based Opadry II coatings on placebo tablets. By manipulating coating parameters during spray application, tablets with varying film attributes were created. A direct correlation between refractive index and coating density was revealed by terahertz surface reflection. It was demonstrated by terahertz pulsed imaging that both coating density and thickness significantly influence hydration and dissolution rates, with density proven as a more promising factor than weight gain alone. The importance of coating parameter control to ensure predictable tablet disintegration and drug release is underscored, with coating density highlighted as a key determinant.