Polymer microspheres for controlled drug release

Freiberg, Stephan; Zhu, Xuhai

doi:10.1016/j.ijpharm.2004.04.013

Cited by 1,173 publications

(721 citation statements)

References 116 publications

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“…15 The release of a drug from polymeric microparticles occurs through different mechanisms: desorption of the drug from the surface of the particles; diffusion of the drug through the pores of the polymeric matrix; erosion of the polymeric matrix; polymer degradation or a combination of different processes. 5,19 As PHB is very slowly degraded, the release profile of a drug from a PHB matrix is generally dependent on drug diffusion rather than on polymer degradation. 20 The results for the PHB molecular weight, pore size distributions and the morphology of the microparticles after the release assay indicated that the release of PXC from PHB microparticles occurs mainly through the two mechanisms: desorption of the drug from the surface of the particles and diffusion of the drug through the pores of the polymeric matrix.…”

Section: Discussionmentioning

confidence: 99%

“…The microparticles are then washed, collected and dried. [4][5][6] The characteristics of microparticles obtained through this technique are affected by process parameters such as solvent, temperature, volume ratio of disperse-continuous phase, type and concentration of the emulsifier, drug/polymer ratio and stirring rate. 7 The solvent removal kinetics can affect the physicochemical properties of the microparticles, in particular the surface morphology and porosity, which in turn affects the rate of drug release.…”

Section: Introductionmentioning

confidence: 99%

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Effect of preparation conditions on morphology, drug content and release profiles of poly(hydroxybutyrate) microparticles containing piroxicam

Bazzo¹,

Lemos‐Senna²,

Gonçalves³

et al. 2008

J. Braz. Chem. Soc.

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No presente estudo foram preparadas micropartículas de poli(hidroxibutirato) contendo piroxicam pela técnica de emulsão-evaporação do solvente. A influência de alguns parâmetros do processo sobre a eficiência de encapsulação do fármaco foi avaliada por meio de um planejamento fatorial do tipo 2 3 . A eficiência de encapsulação do piroxicam variou de 5,5 a 89,8%. Micropartículas ocas e irregulares, contendo cristais de fármaco na superfície, foram obtidas quando se utilizou 5 mL de clorofórmio como fase interna da emulsão. Com o ensaio de liberação in vitro evidenciouse que, após 8 h, todo o fármaco havia sido liberado para o meio. Micropartículas esféricas com superfície externa rugosa e porosa foram obtidas quando se utilizou 20 mL de diclorometano como fase interna e adicionou-se isopropanol à fase externa da emulsão. Essas microesferas foram capazes de controlar a liberação do piroxicam durante 50 h. Os resultados obtidos demonstraram que é possível obter micropartículas com características específicas pela otimização das condições empregadas no processo de encapsulação.In this study, poly(hydroxybutyrate) microparticles containing piroxicam were prepared by the oil-in-water emulsion-solvent evaporation method. The effects of some process conditions on drug content were determined using a 2 3 factorial design. The piroxicam loading efficiency varied from 5.5 to 89.8 %. Hollow and irregular microparticles with drug crystals on their surfaces were obtained when 5 mL of chloroform was used as the internal phase. In the release study, all of the piroxicam was released to the dissolution medium (phosphate buffer pH 7.4) after 8 h. Small spherical microspheres with a rough and porous polymeric matrix were obtained when 20 mL of dichloromethane was used as the internal phase and isopropanol was added to the external aqueous phase. These microspheres controlled the piroxicam release for approximately 50 h. The results demonstrated that it is possible to obtain microparticles with specific characteristics by the optimization of the process conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of preparation conditions on morphology, drug content and release profiles of poly(hydroxybutyrate) microparticles containing piroxicam

Bazzo¹,

Lemos‐Senna²,

Gonçalves³

et al. 2008

J. Braz. Chem. Soc.

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“…Polymer hydrolytic degradation depends on many factors such as the molecular weight, the copolymer composition and the crystallinity of the polymer, all of which control water accessibility to the ester linkage (Anderson et al, 1997;Batycky et al, 1997;Freiberg et al, 2004). A change of one of these parameters will induce a variation in the protein release profile as protein destabilization is related to a large extend to polymer degradation kinetics.…”

Section: Delay Of Polymer Degradationmentioning

confidence: 99%

“…All these properties influence the release of the drug from the delivery system. Among these variables, the morphology of microspheres, especially their porosity, plays a key role in modulating drug release (Freiberg et al, 2004); a large number of pores may greatly increase the rate of drug expulsion (Yang et al, 2000). Porosity is determined during microsphere hardening as the organic solvent evaporates during preparation and is influenced by the preparation temperature, solvent removal rate, and the volume of internal water phase when the common solvent evaporation technique is employed.…”

Section: Preparation Of Porous Microspheresmentioning

confidence: 99%

How to achieve sustained and complete protein release from PLGA-based microparticles?

Giteau

Venier-Julienne

Aubert-Pouëssel

et al. 2008

International Journal of Pharmaceutics

234

184

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One of the most challenging tasks in the delivery of therapeutic proteins from PLGAbased microparticles is the sustained and complete release of the protein in its native form.The mechanisms responsible for incomplete protein release from these devices are numerous and complex; the beneficial effect of different formulations has often been evaluated in vitro.Strategies employed for overcoming protein destabilization during the release step are reviewed in this paper. Proteins have been protected in the deleterious environment by adding stabilizers to the formulation, or by modifying the protein or the polymer. Alternatively, some strategies have aimed at avoiding the formation of the destabilizing environment. As experimental conditions may influence the results from in vitro release studies, we initially report precautions to avoid adverse effects.

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“…Drug is released from the depot over a period of weeks to months, by drug diffusion out of the polymeric matrix and/or by erosion of the matrix. Thus parameters which influence these 2 processes control the drug release profiles [1]; these include polymer chemistry and erosion mechanism, polymer molecular weight, copolymer composition, crystallinity, polymer-drug interactions, excipients, microsphere size and porosity, drug distribution. [1][2].…”

Section: Introductionmentioning

confidence: 99%

An investigation into the influence of drug lipophilicity on the in vivo absorption profiles from subcutaneous microspheres and in situ forming depots

Deadman

Kellaway

Yasin

et al. 2007

Journal of Controlled Release

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Drug lipophilicity is known to have a major influence on in vivo drug absorption from intramuscularly and subcutaneously administered solutions. Indeed, chemical modification to increase drug lipophilicity is used to enable sustained drug release from solutions. In contrast to the wealth of knowledge on drug release from simple solutions, the influence of drug lipophilicity on its release from controlled release formulations, such as, microparticles and in situ forming depots, have not been systematically studied. Controlled release vehicles are designed to 'control' drug release, hence, in vitro studies show negligible influence of drug lipophilicity on release. The situation could however be different in vivo, due to interactions between the vehicle and biological tissue. We therefore investigated the influence of drug lipophilicity on its in vivo release in rats from two controlled release formulations, PLGA microparticles and in situ forming depots. Both systems exhibited a burst drug release. Subsequent to the burst release, we found that lipophilicity did not influence the rate or extent of drug absorption from the two formulations over a 10-day study period, which would imply that drug partitioning out of the depots was not the main mechanism of drug release from both formulations. This study must however be repeated with a greater number of animals to increase its power.

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Polymer microspheres for controlled drug release

Cited by 1,173 publications

References 116 publications

Effect of preparation conditions on morphology, drug content and release profiles of poly(hydroxybutyrate) microparticles containing piroxicam

Effect of preparation conditions on morphology, drug content and release profiles of poly(hydroxybutyrate) microparticles containing piroxicam

How to achieve sustained and complete protein release from PLGA-based microparticles?

An investigation into the influence of drug lipophilicity on the in vivo absorption profiles from subcutaneous microspheres and in situ forming depots

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