Osmotic tablet coatings: Drying stress, mechanical properties and microstructure

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Polymer Science

Background:

• Osmotic tablet coatings control drug release but are prone to cracking during drying and rupture under osmotic pressure.
• Quantification of drying stress, mechanical properties, and microstructure of these coatings is lacking.

Purpose of the Study:

• To rigorously quantify drying stress, Young's modulus, and fracture properties of cellulose acetate-based osmotic tablet coatings.
• To correlate mechanical properties and drying stress with film microstructure.
• To provide guidelines for designing rupture-free osmotic coatings.

Main Methods:

• Measurement of drying stress, Young's modulus, and fracture properties of cellulose acetate films with plasticizers (polyethylene glycol, hydroxypropyl cellulose).
• Scanning electron microscopy (SEM) for imaging film surface and cross-section.
• Analysis of phase separation during drying.

Main Results:

• Phase separation during drying increases pore size, reduces modulus, and lowers peak drying stress.
• Films with strong adhesion resist rupture, while delamination can lead to rupture due to drying stress.
• Plasticizers influence pore size, modulus, and drying stress.

Conclusions:

• Drying stress and mechanical properties are linked to the microstructure of osmotic tablet coatings.
• Film adhesion to the substrate is crucial for preventing rupture.
• Formulators can use these findings to design robust, rupture-free osmotic drug delivery systems.