Behaviour of HPMC compacts investigated using UV-imaging

Area of Science:

• Materials Science
• Pharmaceutical Sciences
• Polymer Chemistry

Background:

• Hydroxypropyl methylcellulose (HPMC) is a widely used polymer in pharmaceutical formulations, particularly for controlled drug release.
• Understanding HPMC's hydration and swelling behavior is crucial for predicting drug release kinetics.
• Current methods for observing polymer behavior in solution can be limited in real-time visualization.

Purpose of the Study:

• To visualize and characterize the behavior of hydroxypropyl methylcellulose (HPMC) in buffer solutions using UV imaging.
• To correlate the observed polymer behavior with rheological measurements to understand drug release mechanisms.
• To investigate the influence of different HPMC viscosity grades on its solution behavior.

Main Methods:

• Real-time UV imaging at 214 nm to observe HPMC behavior in stagnant and flowing buffer solutions.
• Rheological measurements, including steady shear and oscillatory shear tests, to determine polymer characteristics.
• Comparison of two HPMC viscosity grades (15 cP and 50 cP).

Main Results:

• UV imaging identified three distinct phases of HPMC behavior: gel formation, gel expansion, and steady-state conditions.
• A critical polymer concentration was observed, corresponding to the rheological gel point, where the polymer network withstands shear forces.
• Higher viscosity HPMC grades exhibited faster swelling, thicker gel layers, and greater resistance to shear-induced erosion.

Conclusions:

• UV imaging is a suitable technique for both qualitative and quantitative analysis of polymer behavior in solution.
• The study provides insights into critical polymer properties affecting drug release by linking visual HPMC behavior to rheological data.
• Understanding HPMC's gelation and erosion dynamics is key for optimizing drug delivery systems.