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Controlled-release liquid suspensions based on ion-exchange particles entrapped within acrylic microcapsules
M Cuña1, J L Vila Jato, D Torres
1Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Santiago de Compostela, 15706, Santiago de Compostela, Spain.
International Journal of Pharmaceutics
|May 10, 2000
Summary
The oil-in-water method for microencapsulating terbutaline offers superior stability for controlled-release formulations compared to the oil-in-oil method. This aqueous approach preserves drug diffusion and dissolution profiles over six months, unlike the oil-in-oil method which degrades quickly.
Area of Science:
- Pharmaceutical Sciences
- Materials Science
- Drug Delivery Systems
Background:
- Developing stable, controlled-release liquid formulations for anti-asthmatic drugs like terbutaline is crucial for patient compliance and efficacy.
- Eudragit RS/RL polymers are suitable for microencapsulation, but their stability in liquid suspensions requires thorough investigation.
- The choice of microencapsulation method significantly impacts the integrity and performance of drug-loaded microparticles.
Purpose of the Study:
- To formulate terbutaline-loaded ion-exchange resin microcapsules for a controlled-release liquid dosage form using Eudragit RS/RL polymers.
- To evaluate the stability of these microcapsules in a hydroxypropylmethylcellulose suspension over a six-month period.
- To compare the impact of oil-in-oil (o/o) versus oil-in-water (o/w) solvent evaporation methods on microcapsule integrity and drug release.
Main Methods:
- Microencapsulation of terbutaline-loaded ion-exchange resins using modified o/o and o/w solvent evaporation techniques with Eudragit RS/RL.
- Suspension of microcapsules in a hydroxypropylmethylcellulose solution and storage under controlled conditions (20°C, ambient humidity) for 6 months.
- Stability assessment through monitoring drug diffusion, dissolution behavior, and morphological changes via scanning electron microscopy.
Main Results:
- Microcapsules prepared by the o/o method exhibited coating rupture within one day of storage, leading to altered terbutaline release profiles after one week.
- Microcapsules produced via the o/w method maintained coating integrity throughout the 6-month study period.
- The o/w method demonstrated consistent controlled-release profiles for terbutaline, attributed to coating of swollen resin particles, preventing rupture.
Conclusions:
- The oil-in-water (o/w) solvent evaporation method is superior for preparing stable terbutaline microcapsules for controlled-release liquid formulations.
- Microcapsule integrity and sustained drug release are compromised in the oil-in-oil (o/o) method due to resin swelling and coating rupture.
- The aqueous microencapsulation process protects the polymer coating by accommodating swollen resin particles, ensuring long-term formulation stability.