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Increase in the specific surface area of budesonide during storage postmicronization
Vidya Joshi1, Sarvajna Dwivedi, Gary H Ward
1Dura Pharmaceuticals, San Diego, California 92121, USA. vidya_joshi@hotmail.com
Pharmaceutical Research
|February 12, 2002
Summary
Micronized budesonide (a corticosteroid) showed a significant increase in surface area after storage. This phenomenon, driven by particle stress relaxation and fracture, impacts budesonide
Area of Science:
- Pharmaceutical Sciences
- Materials Science
- Particle Engineering
Background:
- Micronization is a critical process for improving the bioavailability of poorly soluble drugs like budesonide.
- Understanding post-processing changes in particle properties is essential for drug formulation and stability.
Purpose of the Study:
- To investigate an anomalous increase in the specific surface area of budesonide after micronization and during storage.
- To elucidate the underlying mechanisms responsible for this observed surface area change.
Main Methods:
- Budesonide was micronized using an air-jet mill.
- Specific surface area and pore volume were determined via nitrogen sorption.
- Porosity was assessed using mercury intrusion porosimetry, and particle size distribution was measured by laser diffraction.
Main Results:
- A significant increase (22 ± 2%) in budesonide surface area was observed upon storage at 25°C post-micronization.
- The rate of surface area increase was temperature-dependent, suggesting stress relaxation.
- Accompanying changes included increased pore volume, a shift in pore size distribution, reduced larger particle sizes, and increased surface roughness.
Conclusions:
- Freshly micronized budesonide exhibits an unusual, significant increase in specific surface area during ambient storage.
- The primary mechanism is attributed to post-micronization stress relaxation, involving intraparticle crack formation, propagation, and subsequent particle fracture.