Studies on the interaction of water with ethylcellulose: Effect of polymer particle size

Agrawal, Anjali; Manek, Rahul V.; Kolling, William M.; Neau, Steven H.

doi:10.1208/pt040460

Cited by 58 publications

(42 citation statements)

References 26 publications

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“…EC is a water-insoluble polymer; it has been widely used in microencapsulation in order to retard the release of many drugs (33)(34)(35)(36). Being hydrophobic in nature (37), EC is expected to prolong the release of 5-ASA from ES100-based microspheres at pHs higher than the threshold of ES100 ionization (pH 7).…”

Section: Microspheres With Varying Drug-to-polymeric-blends Ratiomentioning

confidence: 99%

Influence of Some Formulation Variables on the Optimization of pH-dependent, Colon-targeted, Sustained-release Mesalamine Microspheres

El-Bary¹,

Aboelwafa²,

Sharabi³

2011

AAPS PharmSciTech

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Abstract. The aim of this work was to understand the influence of different formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres prepared by O/O emulsion solvent evaporation method, employing pH-dependent Eudragit S and hydrophobic pHindependent ethylcellulose polymers. Formulation variables studied included concentration of Eudragit S in the internal phase and the ratios between; internal to external phase, drug to Eudragit S and Eudragit S to ethylcellulose to mesalamine. Prepared microspheres were evaluated by carrying out in vitro release studies and determination of particle size, production yield, and encapsulation efficiency. In addition, morphology of microspheres was examined using optical and scanning electron microscopy. Emulsion solvent evaporation method was found to be sensitive to the studied formulation variables. Particle size and encapsulation efficiency increased by increasing Eudragit S concentration in the internal phase, ratio of internal to external phase, and ratio of Eudragit S to the drug. Employing Eudragit S alone in preparation of the microspheres is only successful in forming acid-resistant microspheres with pulsatile release pattern at high pH. Eudragit S and ethylcellulose blend microspheres were able to control release under acidic condition and to extend drug release at high pH. The stability studies carried out at 40°C/75% RH for 6 months proved the stability of the optimized formulation. From the results of this investigation, microencapsulation of mesalamine in microspheres using blend of Eudragit S and ethylcellulose could constitute a promising approach for site-specific and controlled delivery of drug in colon.

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Section: Microspheres With Varying Drug-to-polymeric-blends Ratiomentioning

confidence: 99%

Influence of Some Formulation Variables on the Optimization of pH-dependent, Colon-targeted, Sustained-release Mesalamine Microspheres

El-Bary¹,

Aboelwafa²,

Sharabi³

2011

AAPS PharmSciTech

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“…18 Furthermore, the particle size of EC powder and the porosity in compact EC are the major factors that influence the uptake of water and the dissolution of drug from the compacted form. [19][20] Recently, the unique suitability of EC powders to act as an outer shell has also been explored to directly prepare the press-coated tablet with a special time-controlled rupturing function. 21 This function can be further and effectively controlled by modifying the compression force applied to the outer shell, the amount of outer shell used, and the excipients added to the inner core tablet.…”

Section: Introductionmentioning

confidence: 99%

Hydrophilic excipients modulate the time lag of time-controlled disintegrating press-coated tablets

Lin

2004

AAPS PharmSciTech

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An oral press-coated tablet was developed by means of direct compression to achieve the time-controlled disintegrating or rupturing function with a distinct predetermined lag time. This press-coated tablet containing sodium diclofenac in the inner core was formulated with an outer shell by different weight ratios of hydrophobic polymer of micronized ethylcellulose (EC) powder and hydrophilic excipients such as spray-dried lactose (SDL) or hydroxypropyl methylcellulose (HPMC). The effect of the formulation of an outer shell comprising both hydrophobic polymer and hydrophilic excipients on the time lag of drug release was investigated. The release profile of the press-coated tablet exhibited a time period without drug release (time lag) followed by a rapid and complete release phase, in which the outer shell ruptured or broke into 2 halves. The lag phase was markedly dependent on the weight ratios of EC/SDL or EC/HPMC in the outer shell. Different time lags of the press-coated tablets from 1.0 to 16.3 hours could be modulated by changing the type and amount of the excipients. A semilogarithmic plot of the time lag of the tablet against the weight ratios of EC/SDL or EC/HPMC in the outer shell demonstrated a good linear relationship, with r = 0.976 and r = 0.982, respectively. The predetermined time lag prior to the drug release from a presscoated tablet prepared by using a micronized EC as a retarding coating shell can be adequately scheduled with the addition of hydrophilic excipients according to the time or site requirements.

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“…5 displays the effect of Na-m. on the DSC curves of the most hydrophobic poly(NIPAAm)-based composites. Following the method of Agarwal et al, we also recorded the DSC curve of distilled water for reference [29]. The heat of evaporation of distilled water was determined as 41.74 kJ/mol.…”

Section: Dsc Measurements and Resultsmentioning

confidence: 99%

“…Differential scanning calorimetry (DSC) has been employed to study the states of water in a number of polymer stabilised hydrogel systems [26][27][28][29][30]. The interaction of water with such polymers and its distribution within the gel are critical to the physicochemical behaviour of the gel.…”

Section: Introductionmentioning

confidence: 99%

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Composition dependent changes in the swelling and mechanical properties of nanocomposite hydrogels

et al. 2009

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Abstract. We are synthetized thermo-and pH-sensitive gels, which are then tested as skin extenders. Our aim is the development of copolymer and composite hydrogels that, when implanted under the human skin, swell osmotically and thereby induce skin growth.During the polimerization reaction we are produced copolymers with varyable composition, which are proceed from two acrylic compounds [N-isopropyl-acrylamide (NIPAAm), and acrylamide (AAm)]. The mechanical strength and the swelling stability of the gels are enhanced by the addition of fillers [Na-montmorillonite (Na-m.) and with alkyl-ammonium ion organophilized Na-montmorillonites [(C n -m.), n = 4, 12, 18]. With this method we are synthetized composite-hydrogels. The filler content of composites varies between 1 and 25 wt%.We observed that in the case of composites synthesized with the addition of fillers, relatively low filler contents (1-5 wt%) resulted in more extensive swelling and stronger gel structure.In the course of the experiments the monomer composition of the gels (0/100-100/0 mol% NIPAAm/AAm) and in the case of composites, the quality (montmorillonite and organophilized montmorillonite) and quantity (1-25 wt%) of fillers are varied. The extent of swelling and the viscoelastic properties can be manipulated through the ratios of these parameters.In the case of certain copolymer and composite gels, values of desorption enthalpy (ΔH m ) corresponding to the actual water contents were also determined by thermoanalytical measurements (DSC). Swelling values determined by gravimetry and enthalpies calculated from DSC measurements were found to be in good correlation. Evaluation and comparison of the rheological and DSC results also allowed conclusions to be drawn concerning the types of interaction operating among the three components of the * Corresponding author. E-mail: i.dekany@chem.u-szeged.husystem, i.e. the polymer skeleton, the filler and water molecules. We found that water molecules within the gel matrix are bound to the 3-D polymer lattice with bonds of different strengths and the strength of these interactions are dependent on both hydrophilicity and charge conditions. In the case of hydrophobic NIPAAm composites a more extensive swelling can be achieved by applying montmorillonite fillers with hydrophobized surfaces, whereas in the case of hydrophilic AAm-based composites the use of hydrophilic montmorillonite fillers ensure more extensive swelling.

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Studies on the interaction of water with ethylcellulose: Effect of polymer particle size

Cited by 58 publications

References 26 publications

Influence of Some Formulation Variables on the Optimization of pH-dependent, Colon-targeted, Sustained-release Mesalamine Microspheres

Influence of Some Formulation Variables on the Optimization of pH-dependent, Colon-targeted, Sustained-release Mesalamine Microspheres

Hydrophilic excipients modulate the time lag of time-controlled disintegrating press-coated tablets

Composition dependent changes in the swelling and mechanical properties of nanocomposite hydrogels

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