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Published on: June 14, 2016
Evaluation of enteric matrix microspheres prepared by emulsion-solvent evaporation using scanning electron microscopy
1College of Pharmacy, University of Georgia, Athens, GA 30602, USA.
Journal of Microencapsulation
|January 14, 2004
Summary
Theophylline microspheres made with cellulose acetate butyrate (CAB381-20) alone prevented initial drug release. This polymer formulation created a lag time, suggesting a drug-free layer responsible for near zero-order release profiles.
Area of Science:
- Pharmaceutical Sciences
- Materials Science
- Drug Delivery
Background:
- Theophylline is a widely used bronchodilator, but its rapid release can lead to side effects.
- Microsphere formulations offer potential for controlled drug release, improving therapeutic efficacy.
- Cellulose acetate butyrate (CAB381-20) and cellulose acetate phthalate are polymers investigated for drug encapsulation.
Purpose of the Study:
- To investigate the effect of polymer composition on the surface morphology and drug release characteristics of theophylline microspheres.
- To evaluate the role of surface drug crystallization in the release profile of theophylline microspheres.
- To understand the mechanism behind the near zero-order release profiles observed in theophylline microspheres.
Main Methods:
- Theophylline microspheres were prepared using the emulsion-solvent evaporation method.
- Polymers used included cellulose acetate butyrate (CAB381-20) and mixtures with cellulose acetate phthalate.
- Scanning electron microscopy (SEM) was employed to analyze microsphere surface morphology and internal structure before and during dissolution studies in simulated gastric and intestinal fluids.
Main Results:
- Microspheres prepared solely with CAB381-20 showed no surface drug crystals, unlike those made with polymer mixtures.
- An acid wash effectively removed surface drug from mixed polymer microspheres.
- SEM revealed a drug-free polymer layer on the surface of both CAB381-20 and mixed polymer microspheres, correlating with controlled release.
Conclusions:
- The absence of surface drug crystals on CAB381-20 microspheres is crucial for preventing initial burst release and establishing a lag time.
- A drug-free polymer layer appears to be the primary mechanism responsible for the near zero-order release kinetics observed in these theophylline microsphere formulations.
- Formulation design, specifically polymer choice and resulting surface characteristics, significantly impacts the drug release profile of theophylline microspheres.
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