Magnetic resonance imaging and relaxometry to study water transport mechanisms in a commercially available gastrointestinal therapeutic system (GITS) tablet

The hydration of 4 mg Cardura XL (Pfizer™), a commercially available gastrointestinal therapeutic system (GITS) tablet, was investigated using magnetic resonance imaging (MRI). A short echo time (Te = 2.81 ms) technique for MRI of the hydration of a GITS tablet was implemented. From the MR images, signal intensity profiles were generated and interpreted in the context of diffusive and osmotic transport mechanisms. A distinct transition from diffusive to osmotic transport was measured at a timescale relevant to the measured drug release time. Diffusion and osmotic rate coefficients for water in the drug and polymer sweller layers of the tablet were quantified. Spin–lattice T1 and spin–spin T2 relaxation times of the water signal from within the tablet were measured as a function of hydration time in order to incorporate the effects of relaxation into interpretation of signal intensity and provide unique information on the distribution of water in different physical and chemical environments within the tablet.