Applications of terahertz pulsed imaging to sustained-release tablet film coating quality assessment and dissolution performance

The potential of terahertz pulsed imaging (TPI) to predict the dissolution performance in sustained-release tablets was investigated in this study. Batches of coated tablets with similar weight gain during the coating process at the lab and pilot scales were subjected to non-destructive imaging by TPI and subsequently analysed by dissolution testing. The results from the dissolution tests revealed significant differences in the product performance between the lab and pilot scales (Student t-test, P< 0.05). The model-independent dissolution parameters in the pilot scale showed a prolonged mean dissolution time. This indicated that the pharmaceutical active ingredient was released at a slower rate in the pilot compared to the lab scale. While weight gain measurements (the traditional coating quality parameter), failed to provide an early indication of the product functional performance; terahertz parameters (terahertz electric field peak strength and coating layer thickness) provided insight into the subsequent dissolution behaviour. Correlations between terahertz parameters and dissolution were much stronger than correlations between weight gain and dissolution; with the R2 value for terahertz correlations typically around 0.84 as opposed to 0.07 for weight gain correlations. This study presents the initial finding of correlations between terahertz parameters for assessing the coating quality to the dissolution performance of the coated tablet. The contributing factors for these particular correlations are also discussed.