The use of ultrasound and penetrometer to characterize the advancement of swelling and eroding fronts in HPMC matrices

Microstructural imaging of early gel layer formation in HPMC matrices

“…Hydroxypropylmethylcellulose (HPMC) hydrophilic matrices provide extended drug release through surface diffusion and erosion barrier of hydrated polymer. This is commonly termed a gel layer, but it is more accurately described as a hydrated, gelatinous, entangled polymer chain network 1–6. The dynamic properties of the gel layer have been extensively studied in relation to drug release.…”

“…Colombo et al 10 and Bettini et al 17 have identified the movement of swelling, diffusion and erosion fronts in the established hydrating gel layer using coloured visual aids. HPMC concentration profiles have been measured using light scattering18 and the advancing swelling and eroding fronts within the gel layer have been monitored using ultrasound 1 . 1 H NMR microscopy can be used to measure water self‐diffusion profiles and compare the dynamics of radial and axial swelling,19–22 polymer and drug concentration profiles can also be obtained by this technique 23.…”

Different HPMC Viscosity Grades as Coating Agents for an Oral Time and/or Site‐Controlled Delivery System: An Investigation into the Mechanisms Governing Drug Release

“…Therefore, solvent penetration could also be affected by the rate of water diffusion through the gel barrier that separates the glassy polymer from the bulk medium 22, 23. To take account of the overall phenomena, an experimental procedure commonly employed in the field of hydrophilic matrices for prolonged release was adopted 24–27. Pure Methocel® E5, E50, and K4M tablets provided with a partial impermeable coating were used, so that solvent penetration could take place through one face only, that is, in a single direction.…”

NMR study of molecular dynamics in selected hydrophilic polymers

“…Among them are the cellulose derivatives, mainly hydroxypropyl methyl cellulose (HPMC), and also methyl cellulose (MC) and hydroxypropyl cellulose (HPC). Due to the application in the pharmaceutical industry the hydrophilic polymers are the subjects of many studies by different methods [1][2][3][4][5][6][7]. The interactions of the hydroxypropyl methyl cellulose with solvents were the subject of our MRI study [7].…”