Non-destructive prediction of enteric coating layer thickness and drug dissolution rate by near-infrared spectroscopy and X-ray computed tomography.

The coating layer thickness of enteric-coated tablets is a key factor that determines the drug dissolution rate from the tablet. Near-infrared spectroscopy (NIRS) enables non-destructive and quick measurement of the coating layer thickness, and thus allows the investigation of the relation between enteric coating layer thickness and drug dissolution rate. Two marketed products of aspirin enteric-coated tablets were used in this study, and the correlation between the predicted coating layer thickness and the obtained drug dissolution rate was investigated.

Delay effect of magnesium stearate on tablet dissolution in acidic medium.

Magnesium stearate (Mg-St) is a common lubricant used for solid pharmaceutical formulations and is known for its property to cause delay of tablet dissolution. In this study, the mechanism underlying the delay caused by Mg-St was investigated with model metformin hydrochloride (HCl) tablets containing Mg-St by using the stationary disk method, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). The results revealed the process and mechanism of delay: the exposed amount of Mg-St on the tablet surface increases during the dissolution process, and tablet dissolution is limited by the diffusion of Mg-St.