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Polyvinyl alcohol succinate and glutarate coprecipitated with ibuprofen as pH-sensitive drug delivery systems
No full textPolyvinyl alcohol was substituted with succinic anhydride and glutaric anhydride to obtain polymers with pH-dependent solubility. The polymers were assessed as potential substrate materials for pH-dependent drug delivery systems. Ibuprofen was used as a model drug, where pH-dependent release could avoid its gastric side effects. Coprecipitates of the drug and the polymer at 1/1, 2/1 and 3/1 w/w ratios were prepared and release of the drug from the coprecipitates was evaluated in vitro at pH 2.0, 5.5, 7.0, 8.0. The results indicated the ability of the substituted polymers to hinder drug release in acidic aqueous environments while allowing release at higher pH values
Self-assembling poly(vinyl alcohol) derivatives, interactions with drugs and control of release
No full textThe self-assembling properties of poly(vinyl alcohol) substituted with 2-hydroxypropyltrimethylammonium and with acyl chains of different molecular weights (butyryl, capryloyl, lauroyl, or myristoyl) were evaluated to assess the conditions favoring interaction with a poorly soluble drug such as indomethacin to increase its availability. To evaluate the effect of drug-polymer interactions on the solubility of the drug, phase-solubility diagrams were obtained from each substituted polymer at pH 2.0, 5.5, and 7.4 in the presence of indomethacin. To evaluate the availability of the free drug in solution, release profiles of the free drug from drug-polymer physical mixtures were obtained by a dissolution-diffusion apparatus containing a dialysis membrane allowing diffusion of the free drug towards a receiving phase where its concentration was determined over time. The phase-solubility diagrams revealed increasing drug solubility on increasing the polymer concentration. The drug-polymer affinity was slightly increased by lengthening the chain of the substituent on the polymer and was strongly increased by raising the pH of the aqueous phase. The thermodynamic evaluation of the drug-polymer interactions indicated that the interaction is enthalpically driven while the increase in drug-polymer affinity with increasing chain length could be attributed to an entropic contribution. The free drug availability from the drug-polymer systems increased on enhancing the drug-polymer affinity because it corresponded to an increase in the solubilizing effect of the polymer on the drug. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association
pH-sensitive polymeric physical-mixture for possible site-specific delivery of ibuprofen
No full textDelivery of drugs to the large bowel has been extensively investigated during the last decade. The aim of this work was to study polymethacrylic acid-co-methylmethacrylate substituted with fatty acids (lauric, myristic, palmitic and stearic) at 20% substitution degree (PMA-LAUR20, PMA-MIR20, PMA-PALM20 and PMA-STEA20) or 40% substitution degree (PMA-LAUR40, PMA-MIR40, PMA-PALM40 and PMA-STEA40) for preparing a pH-sensitive physical mixture for site-specific delivery of ibuprofen chosen as a model drug. The preparation and characterization of the substituted polymers were described. In vitro release studies were conducted at different pH levels (3 h at pH 2.0, 2 h at pH 5.5, 4 h at pH 7.4 and until 24 h at pH 7.0) and phase-solubility diagrams of ibuprofen with the different substituted polymers were obtained at pH 7.0 to obtain information on the influence of amphiphilic polymers in increasing drug solubility and drug availability in the colon. © 2003 Elsevier Science B.V. All rights reserved
Effect of chitosan on progesterone release from hydroxypropyl-β-cyclodextrin complexes
No full textAn inclusion complex composed of progesterone (Prog) and hydroxypropyl-β-cyclodextrin (HPβCD) was prepared by the spray-drying and freeze-drying methods. Prog alone and its inclusion complex with HPβCD were incorporated into chitosan by spray-drying and freeze-drying. The inclusion complex was characterized by IR and DSC. The inclusion complex was investigated in solution by phase solubility diagrams and stability constant was determined at pH 7.4 and at different temperatures (10, 25 and 37°C) to obtain the thermodynamic parameters of inclusion. The results indicate that the Prog-HPβCD inclusion complex is more water soluble than Prog alone. Release data from all samples showed significant improvement of the dissolution rate of Prog and a controlled release is obtained in the presence of chitosan. © 2003 Elsevier Science B.V. All rights reserved
Substituted polyvinylalcohol as a drug carrier for β-carotene
No full textThe objective of this study was to evaluate the in vitro characteristics of polyvinylalcohol 10,000 (PVA10,000) and polyvinylalcohol 15,000 (PVA15,000) substituted with different alkyl chains (Iodododecane, Bromotetradecane) and crosslinked with Bis-chloro-ethoxy-ethane as an injectable drug carrier. β-carotene was used as a lipophilic model drug. Physical mixtures of the drug and the spray-dried polymers were prepared and the release of the drug from the mixtures was evaluated in vitro at pH 7.4. The results indicated that the substituted PVA10,000 and PVA15,000 provided faster drug release with respect to the pure drug at pH 7.4. In particular, among the substituted PVA used, PVA10,000 and PVA15,000 substituted with Iodododecane and crosslinked with Bis-chloro-ethoxy-ethane improved drug release. © 2003 Elsevier B.V. All rights reserved
Substituted poly(methyl vinyl ether-alt-maleic anhydride) for the release control and targeting of methotrexate
No full textPoly(methyl vinyl ether-alt-maleic anhydride) substituted with cholamine (CA), aminoethylcholamine (AECA), or aminooctylcholamine (AOCA) at different substitution degrees, were used for methotrexate (MTX) complexation. The solid complexes, isolated by precipitation from the preparative mixture, showed lower fractional releases at ph 7.4 than at 5.5. This was ascribed to the establishment of ionic interactions between the ionized carboxyls of both the polymer and the drug and the quaternary ammonium groups of the substituents (CA, AECA, AOCA) inducing polymer self-aggregation and thus complex stabilization. The fractional release in pH 7.4 decreases with the increase in the substitution degree until a minimum characteristic for each substituent analyzed is reached and then rises with the increase in substitution degree. The minimum release at pH 7.4 was observed in the presence of AECA at the degree of substitution corresponding to 0.35 mole of substituent per mole of dimer (methyl vinyl ether-maleic anhydride). None of the substituted polymers studied had any haemolytic effect, indicating good biocompatibility
Chitosan salts as nasal sustained delivery systems for peptidic drugs
No full textThe aim of this study was to describe a sustained drug release system based on chitosan salts for vancomycin hydrochloride delivery. Chitosan lactate, chitosan aspartate, chitosan glutamate and chitosan hydrochloride were prepared by spray-drying technique. Vancomycin hydrochloride was used as a model peptidic drug, the nasal sustained release of which should avoid first-pass metabolism in the liver. This in-vitro study evaluated the influence of chitosan salts on the release behaviour of vancomycin hydrochloride from the physical mixtures at pH 5.5 and 7.4. In-vitro release of vancomycin was retarded by chitosan salts and, in particular, chitosan hydrochloride provided the lowest release of vancomycin
Physically cross-linked chitosan hydrogels as topical vehicles for hydrophilic drugs
No full textPhysically cross-linked chitosan hydrogels with lauric, myristic, palmitic or stearic acid were prepared by freeze-drying and have been studied for topical use. This study selected propranolol hydrochloride as a hydrophilic model drug to design a transdermal delivery system. We evaluated the effect of the nature of the cross-linker on drug permeation through porcine skin and the main permeation parameters (diffusion coefficient, flux and lag time) were calculated. All the chitosan hydrogels analysed provided more transcutaneous permeation of propranolol hydrochloride than the corresponding solution of the commercial drug. Among the different chitosan vehicles, chitosan-laurate and chitosan-myristate hydrogels enhanced lyophilised drug diffusion through the skin with respect to chitosan-palmitate and chitosan-stearate hydrogels. This can been explained by the interaction of the hydrogels with the stratum corneum, increasing the solubility of the drug in the skin
Fatty acid substituted polyvinyl alcohol as a supporting material for microsphere preparation
No full textPolyvinyl alcohol, substituted with lauric, myristic, palmitic, and stearic acids at different substitution degrees was employed for the preparation of biodegradable microspheres containing progesterone or indomethacin. A solvent extraction/method was followed, starting from an oil-in-water dispersion containing the polymer and drug in the inner phase. Microspheres were obtained with high loading efficiency, whose release properties were dependent on the nature of the acyl substituent and the substitution degree. Kinetics approaching zero-order were obtained for the most hydrophile microspheres such as those based on the least substituted polymers and lowest molecular weight substituents. The hydrophilicity of these systems hindered protein absorption on their surface, suggesting their suitability for parenteral use
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