Viscosity of polymer solution phase and other factors controlling the dissolution of theophylline microspheres prepared by the emulsion solvent evaporation method

Obeidat, Wasfy M.; Price, James C.

doi:10.1080/0265204021000022716

Cited by 16 publications

(14 citation statements)

References 7 publications

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“…The most commonly used particle preparation procedure enabling drug encapsulation is emulsion-solvent evaporation (Obeidat and Price, 2003;Ogawa et al, 1988;Watts et al, 1990). This methodology has been applied to a diverse range of lipophilic drugs (Juni et al, 1985;Kim et al, 2005;Ruan and Feng, 2003), however as such is not suitable for the encapsulation of hydrophilic drugs and biomolecules (Jalil and Nixon, 1990).…”

Section: Introductionmentioning

confidence: 99%

Encapsulation and release ofα-chymotrypsin from poly(glycerol adipate-co-ω-pentadecalactone) microparticles

Gaskell¹,

Hobbs²,

Rostron³

et al. 2008

Journal of Microencapsulation

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Polymer based microparticles are increasingly becoming of interest for a variety of applications including drug delivery. Recently poly(glycerol adipate) (PGA) and poly(glycol adipate-co--pentadecalactone) have shown promise for delivery of dexamethasone phosphate and ibuprofen. In this paper the copolyester poly(glycol adipate-co--pentadecalactone) was evaluated as a colloidal delivery system for encapsulated therapeutic proteins. Enzyme containing microparticles were prepared via the double water-in-oil-in-water (w/o/w) emulsion-solvent evaporation methodology. -chymotrypsin was used as a model proteolytic enzyme and its transfer was monitored during the emulsification process, in addition to in vitro release from formed particles. On average 22.1g protein per 1mg polymer was encapsulated, although gradual loss of activity of the protein, once released, was recorded. The work presented shows the potential of this polyester as a delivery system for enzymes via microparticles, with improvements to the system achievable via polymer and process optimisation. The pendant hydroxyl groups on the polymer backbone provide future capacity for tailored alteration of the physical and chemical properties of the polymer, in addition to covalent attachment of various compounds.

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Section: Introductionmentioning

confidence: 99%

Encapsulation and release ofα-chymotrypsin from poly(glycerol adipate-co-ω-pentadecalactone) microparticles

Gaskell¹,

Hobbs²,

Rostron³

et al. 2008

Journal of Microencapsulation

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“…These observations could be attributed to the fact that an increase in organic phase viscosity would hold the drug firmly inside the microsphere so that the diffusion of the drug is slowed (2).…”

Section: Effect Of Microsphere Size and Polymer Concentration/ Viscosmentioning

confidence: 99%

“…Theophylline, a methylxanthine alkaloid that is used in the treatment of asthma as a bronchodilator, has a narrow therapeutic index in the range of 5-20 μg/ml and has therefore received a considerable amount of attention in oral sustained release formulations (1)(2)(3)(4). The development of a dosage form such as a microsphere is believed to enhance tolerance and to control the release of theophylline to achieve a safe therapeutic concentration in the blood.…”

Section: Introductionmentioning

confidence: 99%

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Investigations on the Physical Structure and the Mechanism of Drug Release from an Enteric Matrix Microspheres with a Near-Zero-Order Release Kinetics Using SEM and Quantitative FTIR

Obeidat

Al-Zoubi

2009

AAPS PharmSciTech

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Abstract. The objectives of this study were to evaluate the physical structure and the release mechanisms of theophylline microspheres made of Eudragit S 100 polymer as an enteric polymer, combined with a nonerodible polymer, Eudragit RL 100. In the preparation process, polymer combinations (1:1) were dissolved in an organic solvent mixture composed of acetone and methanol at a specific ratio containing a theoretical drug loading of approximately 15%. Two microsphere formulations (LS1 and LS2) were prepared at two different total polymer concentrations (10% in LS1 and 12.7% in LS2). Dissolution studies were carried out using US Pharmacopeia Dissolution Apparatus II in an acidic medium for 8 h and in an acidic medium (2 h) followed by a slightly basic-buffered medium for 10 h. Both LS1 and LS2 microsphere formulations produced particles that were spherical in shape and had very narrow size distributions with one size fraction comprising 70-80% of the yield. Scanning electron microscopy and quantitative Fourier transform infrared were used for microsphere physical structure evaluation. Except for the absence of drug crystals, photomicrographs of both LS microspheres after dissolution in pH 1.2 and 7.2 buffer solutions were similar to those before dissolution. Dissolution results indicated the ability of LS microspheres to minimize drug release during the acid stage. However, in the slightly basic medium that followed the acidic stage, the drug release was sustained and controlled in its kinetics and data fitted to Peppas equation indicated a case II transport suggesting that the drug release is mainly through swelling/erosion mechanism.

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“…The effects of polymer molecular weight and viscosity grade have been studied by several workers (Deasy et al 1980;Bodmeier et al 1991). Recently, there was a study on the effect of the polymer solution viscosity on mocrosphere dissolution properties prepared by the same method and the results suggested a relationship between apparent viscosity of polymer solution and the dissolution properties of microspheres (Obeidat and Price 2003). However, polymers used in the previous study were of similar composition, differing only in the molecular weights.…”

Section: Introductionmentioning

confidence: 95%

Preparation andin vitroevaluation of propylthiouracil microspheres made of Eudragit RL 100 and cellulose acetate butyrate polymers using the emulsion-solvent evaporation method

Obeidat

Price

2005

Journal of Microencapsulation

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The objectives of this investigation are to evaluate the encapsulation efficiency of the anti-thyroid agent 6-n-propyl-2-thiouracil using two polymers of different characteristics (cellulose acetate butyrate polymer, (CAB-551-0.01) and ammonio methacrylate copolymer (Eudragit RL 100) and to study the effect of this encapsulation on the drug release properties. Polymers were used separately and in combination to prepare different microspheres. Also, the effect of polymer solution phase viscosity was studied for each of the polymers and for their combinations. An Ostwald viscometer was used to evaluate the relative viscosities of polymer solution phases and their combinations. Microspheres with 25% theoretical drug loading of 6-n-propyl-2-thiouracil core material were prepared by the emulsion solvent evaporation method. Microspheres prepared from CAB-551-0.01, which has higher relative polymer phase viscosity than Eudragit RL 100, showed significantly lower drug release rates and a noticeable lag time. Polymer combinations of CAB-551-0.01 and Eudragit RL 100 (1:1) showed an interesting synergistic increase in relative polymer solution viscosities at all concentrations. Unlike microspheres prepared from the two polymers separately which follow Higuchi spherical matrix release kinetics, microspheres prepared using a combination (1:1) of the two polymers showed near zero order with faster rates compared to those prepared using CAB-551-0.01 equivalent polymer concentrations. The results of this study suggest that 6-n-propyl-2-thiouracil was successfully and efficiently encapsulated and release rates of matrix microspheres are related to polymer solution phase viscosity, but when polymer combinations were used other factors such as structural effects must be considered.

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Viscosity of polymer solution phase and other factors controlling the dissolution of theophylline microspheres prepared by the emulsion solvent evaporation method

Cited by 16 publications

References 7 publications

Encapsulation and release ofα-chymotrypsin from poly(glycerol adipate-co-ω-pentadecalactone) microparticles

Encapsulation and release ofα-chymotrypsin from poly(glycerol adipate-co-ω-pentadecalactone) microparticles

Investigations on the Physical Structure and the Mechanism of Drug Release from an Enteric Matrix Microspheres with a Near-Zero-Order Release Kinetics Using SEM and Quantitative FTIR

Preparation andin vitroevaluation of propylthiouracil microspheres made of Eudragit RL 100 and cellulose acetate butyrate polymers using the emulsion-solvent evaporation method

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