基于HPMCAS载体的依非韦伦固体分散体溶出模式研究

目的 以依非韦伦为原料药、不同规格（L、M、H）HPMCAS为载体，采用喷雾干燥法制备固体分散体并对其溶出模式进行初步探究。方法 通过X射线粉末衍射（XRPD）、扫描电子显微镜（SEM）对固体分散体理化性质进行制剂学表征；以动力溶解度为指标考察不同药载比、不同规格HPMCAS固体分散体的溶出情况；通过粒度分析仪和透射电子显微镜（TEM）、SEM探讨固体分散体溶出时的不同模式。结果 XRPD分析显示，固体分散体中药物以无定形的形态分散在HPMCAS中；SEM分析显示，L、M、H规格HPMCAS与依非韦伦形成的固体分散体均具有"萎缩葡萄干"形态；在pH 6.8磷酸缓冲盐溶液中溶出时，药载比1：6的固体分散体溶出好，药载比1：1.5的固体分散体溶出差且相同药载比时L规格HPMCAS的固体分散体溶出更快。结论 以不同规格HPMCAS为载体制备的依非韦伦固体分散体在pH 6.8磷酸缓冲盐溶液中溶出时，存在多种溶出模式。药载比1：6时，L、M规格HPMCAS的固体分散体以药物纳米颗粒的形式溶出；药载比1：1.5时，L、M规格HPMCAS的固体分散体存在类似溶蚀的溶出模式，药物从载体骨架中释放。     

Nanoscale thermal analysis of pharmaceutical solid dispersions

Formation of a solid solution of a drug in a water-soluble polymer is one of the primary techniques used to improve the dissolution rate and thus bioavailability of a poorly water-soluble drug. Understanding and detecting the state of the drug inside such a polymer matrix is critically important since issues such as drug stability, safety and efficacy can be greatly affected. In this study, two model formulations were prepared containing low and high levels of drug content. The heterogeneity of the formulations has been investigated using a novel nanothermal analysis technique. This technique has demonstrated a promising capability for imaging and quantitatively characterising the nanoscale properties of solid dispersion formulations.     

Preparation and characterization of spray-dried valsartan-loaded Eudragit® E PO solid dispersion microparticles

The purpose of this study was to develop the immediate release stomach-specific spray-dried formulation of valsartan (VAL) using Eudragit^® E PO (EPO) as the carrier for enhancing dissolution rate in a gastric environment. Enhanced solubility and dissolution in gastric pH was achieved by formulating the solid dispersion using a spray drying technique. Different combinations of drug–polymer–surfactant were dissolved in 10% ethanol solution and spray-dried in order to obtain solid dispersion microparticles. Use of the VAL–EPO solid dispersion microparticles resulted in significant improvement of the dissolution rate of the drug at pH 1.2 and pH 4.0, compared to the free drug powder and the commercial product. A hard gelatin capsule was filled with the VAL–EPO solid dispersion powder prior to the dissolution test. The increased dissolution of VAL from solid dispersion microparticles in gastric pH was attributed to the effect of EPO and most importantly the transformation of crystalline drugs to amorphous solid dispersion powder, which was clearly shown by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and powder X-ray diffraction (P-XRD) studies. Thus, VAL, a potential antihypertensive drug in the form of a solid dispersion microparticulate powder, can be effectively delivered in the immediate release dosage form for stomach-specific drug delivery.     

Investigating the molecular dissolution process of binary solid dispersions by molecular dynamics simulations

Dissolution molecular mechanism of solid dispersions still remains unclear despite thousands of reports about this technique. The aim of current research was to investigate the molecular dissolution mechanism of solid dispersions by molecular dynamics simulations. The formation of ibuprofen/polymer solid dispersions was modeled by the simulated annealing method. After that, the models of solid dispersions were immersed into the water box with 25–30 Å thicknesses and 50–100 ns MD simulations were performed to all systems. Simulation results showed various dissolution behaviors in different particle sizes and various polymers of solid dispersions. Small-sized particles of solid dispersions dissolved quickly in the water, while the large particles of PEG or PVP-containing solid dispersions gradually swelled in the dissolution process and drug molecules may aggregate together. In the dissolution process, the carboxylic groups of ibuprofen molecules turned its direction from polymer molecules to external water box and then the drug molecules left the polymer coils. At the same time, polymer coils gradually relaxed and became free polymer chains in the solution. In addition, solid dispersion with poloxamer could prevent the precipitate of drug molecules in the dissolution process, which is different from those of PEG or PVP-containing systems. This research provided us clear images of dissolution process of solid dispersions at the molecular level.     

Formation and characterization of solid dispersions of piroxicam and polyvinylpyrrolidone using spray drying and precipitation with compressed antisolvent

Solid dispersions of a poorly water-soluble drug piroxicam in polyvinylpyrrolidone (PVP) were prepared by precipitation with compressed antisolvent (PCA) and spray drying techniques. Physicochemical properties of the products and drug-polymer interactions were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry, etc. Piroxicam was found amorphously dispersed in both solid dispersion systems with the drug to polymer weight ratio of 1:4. Spectra data indicated the formation of hydrogen bonding between the drug and the polymer. Both techniques evaluated in this work resulted in improved dissolution of piroxicam. By comparison, PCA-processed solid dispersions showed distinctly superior performance in that piroxicam dissolved completely within the first 5 min and the dissolution rate was at least 20 times faster than raw drug did within the first 15 min. PCA processing could provide an effective pharmaceutical formulation technology to improve the bioavailability of poorly water-soluble drug.     

介孔二氧化硅纳米粒的制备及对载药与药物溶出度的影响

目的为提高水难溶性药物的分散性及溶出度,制备介孔二氧化硅纳米粒作为水难溶性药物的载体。方法探索得到简单有效地制备球状介孔二氧化硅纳米粒的工艺条件,采用扫描电镜及氮气吸附-脱附等手段分析表征载体的外观形貌,比表面积及孔径分布,并选取水难溶性药物西洛他唑作为模型药物,以溶剂浸渍挥干法载药制得药物固体分散体,采用热分析、氮气吸附-脱附曲线以及溶出度实验研究药物固体分散体的基本性质。结果制得的二氧化硅载体的形貌近球状,粒径大小分布在200～250 nm,载体的比表面积最高可达1 101.54 m2.g-1,孔径分布主要集中在3.0～4.0 nm。载药过程对西洛他唑在载体中的存在形式没有影响,固体分散体中西洛他唑的溶出度得到显著提高,当药物与载体的质量比为1∶3时,药物60 min累计溶出达85%。结论介孔二氧化硅纳米粒有望成为水难溶性药物的优良载体。     

Preparation and Characterization of Nanofibers Containing Amorphous Drug Dispersions Generated by Electrostatic Spinning

Purpose. We assessed the application of water-soluble polymer-based nanofibers prepared by electrostatic spinning as a means of altering the dissolution rate of the poorly water-soluble drug, itraconazole. Methods. Organic solvent-based solutions of itraconazole/HPMC mixtures were electrostatically spun at 16 and 24 kV. The formed nanofibers were collected as a non-woven fabric. The samples were analyzed by scanning electron microscopy, differential scanning calorimetry, and dissolution rate. Results. Scanning electron microscopy showed fiber diameters of 1-4 m and 300-500 nm depending on the applied voltage. Differential scanning calorimetry measurements found that the melting endotherm for itraconazole was not present, suggesting the formation of an amorphous solid dispersion or solution. Dissolution studies assessed several presentations including direct addition of the non-woven fabrics to the dissolution vessels, folding weighed samples of the materials into hard gelatin capsules and placing folded material into a sinker. Controls included a physical mixture as well as solvent cast and melt extruded samples. Electrospun samples dissolved completely over time with the rate of dissolution depending on the formulation presentation and drug to polymer ratio. The physical mixture did not appreciably dissolve in these conditions. Conclusions. The application of electrostatic spinning to pharmaceutical applications resulted in dosage forms with useful and controllable dissolution properties.     

改善难溶性药物功效的一种新型给药系统——干酏剂的研究进展

干酏剂是一种将乙醇和药物同时包裹入水溶性聚合物壳内的固态微囊.乙醇的潜溶剂作用及喷雾干燥工艺可能产生的无定形药物,有利于包裹于干酏剂中的水难溶性药物快速分散并溶解于水性介质中,从而提高其溶出速率和生物利用度.本文综合近年来干酏剂研究的主要文献,从干酏剂的制剂成型工艺及机制、对难溶性药物体外溶出、体内吸收及生物利用度的影响,以及基于干酏剂的剂型设计及应用做一综述.     

Free flowing solid dispersions of the anti-HIV drug UC 781 with Poloxamer 407 and a maximum amount of TPGS 1000: Investigating the relationship between physicochemical characteristics and dissolution behaviour

Solid dispersions and physical mixtures made up of the poorly water-soluble drug UC 781, a polymer and a surfactant were prepared to contribute to the understanding of the relationship between physicochemical characteristics and dissolution behaviour. In addition, to facilitate downstream processing while still favouring drug dissolution to a maximum extent, formulation conditions were investigated to obtain a free flowing powder which contains a maximum amount of surfactant. Poloxamer 407, a polyethylene-polypropylene glycol block copolymer, was selected as a suitable polymer based on UC 781 supersaturation results. d-Alpha-tocopheryl polyethyleneglycol succinate 1000 (TPGS 1000) was preferred as a surfactant since it increased UC 781 dissolution when formulated in a self-micro emulsifying drug delivery system (SMEDDS), as compared to TPGS 400, TPGS 4000 and TPGS 6000. Based on flow properties, a TPGS 1000/Poloxamer 407 ratio of 80/20 was used to prepare solid dispersions by spray drying. Pure drugs, physical mixtures and solid dispersions were characterized by differential scanning calorimetry and X-ray powder diffraction. Eutectic phase behaviour was obtained in which the relative distribution of the polyethylene glycol folding was dependent on UC 781 concentration. Drug release was markedly increased when formulated as a solid dispersion with Poloxamer 407 and TPGS 1000. Formulation of solid dispersions did however not further improve the drug dissolution rate compared to that of physical mixtures. Nonetheless, variability of dissolution results was considerably reduced upon solid dispersion formulation.     

Stereospecific oxidation of the (S)-enantiomer of RS-8359, a selective and reversible monoamine oxidase A (MAO-A) inhibitor, by aldehyde oxidase

In a previous paper by the authors on RS-8359, a new selective and reversible monoamine oxidase A (MAO-A) inhibitor, it was reported that the (S)-enantiomer of RS-8359 is rapidly eliminated from rats, monkeys and humans as a result of the formation of a 2-oxidative metabolite. The present study investigates the properties of the enzyme responsible for the 2-oxidation of RS-8359. Subcellular localization, cofactor requirement and the inhibitory effects of typical compounds were studied using rat liver preparations. In addition, the enzyme was purified from rat liver cytosol for further characterization. The enzyme activity was localized in the cytosolic fraction without the need for any cofactor and was extensively inhibited by menadione, chlorpromazine and quinacrine. The purified enzyme was also a homodimer with a monomeric molecular weight of 140 kDa and it had an A280/A450 ratio of 5.1 in the absorption spectrum. The results suggest that the enzyme responsible for the biotransformation of RS-8359 to give the 2-keto derivative is aldehyde oxidase (EC 1.2.3.1). The reaction of aldehyde oxidase is highly stereoselective for the (S)-configuration of RS-8359 and the (9R)-configuration of cinchona alkaloids.     

Particle design of tolbutamide in the presence of soluble polymer or surfactant by the spherical crystallization technique: improvement of dissolution rate

Poorly soluble crystals of tolbutamide were modified in the presence of a soluble polymer or surfactant by the spherical crystallization technique, the objective being to improve the dissolution rate and to transform platelet crystals into spherical agglomerates. An HCI solution was added to a tolbutamide:NaOH solution containing a water-soluble polymer or surfactant. The tolbutamide crystals were agglomerated with either and were free flowing and spherically compact. The size of the crystals of the agglomerate depended on the viscosity of the solvent and adsorption of the surfactant onto the crystal surface. The tolbutamide-agglomerated crystals dissolved isotropically, with no evidence of disintegration. The dissolution process was described in terms of the Hixson-Crowell equation. The dissolution rate of the agglomerate was 8 times faster than that of conventionally crystallized tolbutamide. Therefore, the solubility and flow-ability of tolbutamide can be improved using the spherical crystallization technique.     

Comparison of surface modification and solid dispersion techniques for drug dissolution

Surface modification and solid dispersion formulations using hydrophilic excipients can significantly alter the dissolution behaviour of hydrophobic drug materials. The effect of these techniques used individually and in combination on the dissolution properties of the hydrophobic drug, phenylbutazone (PB), are compared. PB was treated with a poloxamer, Synperonic((R)) F127 by an adsorption method. Solid dispersions (10 and 20% w/w) were prepared with untreated PB or PB previously modified with Synperonic((R)) F127 (PBT) in molten F127. Dissolution tests of capsule formulations of PB, PBT and solid dispersion formulations, in pH 6.4 buffer at 37+/-0.5 degrees C demonstrated that after 140 min, release of PB was 16.7%, but 71.4% from the solid dispersion, whereas from the PBT formulation 85.6% was released. The Synperonic((R)) F127 content of PBT was only 0.05% of that in the solid dispersion formulation which suggests that it is the nature of the drug polymer contact rather than the amount of polymer which is more critical in influencing dissolution behaviour. Comparison of PBT and the 10% w/w solid dispersion of PBT in F127 showed similar amounts of drug in solution after 140 min. However there was a significantly higher release rate for PBT. Both formulation techniques offer significant improvements in drug release over untreated PB, and a combination of techniques changes the rate but not the extent of release in comparison with the surface modification technique alone.     

Stereospecific oxidation of the (S)-enantiomer of RS-8359, a selective and reversible monoamine oxidase A (MAO-A) inhibitor,by aldehyde oxidase

In a previous paper by the authors on RS-8359, a new selective and reversible monoamine oxidase A (MAO-A) inhibitor, it was reported that the (S)-enantiomer of RS-8359 is rapidly eliminated from rats, monkeys and humans as a result of the formation of a 2-oxidative metabolite. The present study investigates the properties of the enzyme responsible for the 2-oxidation of RS-8359. Subcellular localization, cofactor requirement and the inhibitory effects of typical compounds were studied using rat liver preparations. In addition, the enzyme was purified from rat liver cytosol for further characterization. The enzyme activity was localized in the cytosolic fraction without the need for any cofactor and was extensively inhibited by menadione, chlorpromazine and quinacrine. The purified enzyme was also a homodimer with a monomeric molecular weight of 140?kDa and it had an A₂₈₀/A₄₅₀ ratio of 5.1 in the absorption spectrum. The results suggest that the enzyme responsible for the biotransformation of RS-8359 to give the 2-keto derivative is aldehyde oxidase (EC 1.2.3.1). The reaction of aldehyde oxidase is highly stereoselective for the (S)-configuration of RS-8359 and the (9R)-configuration of cinchona alkaloids.     

Solid Dispersions Prepared by Continuous Cogrinding in an Air Jet Mill

Embedding a poorly water-soluble drug as a solid dispersion in a hydrophilic carrier by cogrinding is a possible strategy for enhancing the drug dissolution rate. Although general interest in continuous processes for manufacturing drug formulations has increased, many publications still focus on batch processes. The jet mill used in this study is a promising tool for continuous cogrinding. Investigation of different drug-to-carrier ratios (griseofulvin/mannitol) demonstrated that a drug load of 10% is best suited to investigate the enhanced dissolution behavior. To gain deeper insight into the underlying mechanisms, the coground dispersion is compared with different physical mixtures in terms of physicochemical properties and dissolution behavior. Differential scanning calorimetry and X-ray powder diffraction were used to verify the crystalline structure of the coground formulation. On the basis of the Hixson-Crowell model, particle size reduction was ruled out as the main reason for dissolution enhancement. An increase of surface free energies because of grinding is shown with contact angle measurements. Confocal Raman microscopy investigations revealed the drug's bulk dispersity in the coground formulation as an additional factor for the increased dissolution rate. In conclusion, the continuous cogrinding approach is a promising technique to prepare the drug in a rapidly dissolving, yet crystalline, form.     

托伐普坦固体分散体的制备及体外溶出特性考察

目的 采用固体分散技术提高难溶性药物托伐普坦的体外溶出度。方法 选用聚维酮K_29/32为载体材料,以溶剂蒸发法制备托伐普坦固体分散体。采用差示扫描量热法(DSC)、X-射线粉末衍射法(XRPD)对所得固体分散体进行鉴定, 并进行溶解度、体外溶出实验。结果 固体分散体的DSC 图谱及X-射线粉末衍射确定了托伐普坦以无定形态分散在载体中, 体外溶解实验表明其溶出较原料药、物理混合物均有明显提高。结论 将托伐普坦与PVP K_29/32制成固体分散体,其分散状态发生了改变,溶出性能明显提高。     

A comparative in vitro assessment of the drug release performance of pH-responsive polymers for ileo-colonic delivery

The aim of this study was to investigate the in vitro dissolution characteristics of pH-responsive polymers in a variety of simulated fluids. Prednisolone tablets were fabricated and coated with the following polymer systems: Eudragit S (organic solution), Eudragit S (aqueous dispersion), Eudragit FS (aqueous dispersion) and Eudragit P4135 (organic solution). Dissolution tests were conducted using a pH change method whereby tablets were transferred from acid to buffer. Three different buffer media were investigated: two compendial phosphate buffers (pH range 6.8-7.4) and a physiological buffer solution (Hanks buffer) with very similar ionic composition to intestinal fluid (pH 7.4). There was considerable drug release from tablets coated with Eudragit P4135 in acid, prompting discontinuation of further investigations of this polymer. Eudragit S (organic solution), Eudragit S (aqueous dispersion) and Eudragit FS on the other hand prevented drug release in acid, though subsequent drug release in the buffer media was found to be influenced by the duration of tablet exposure to acid. At pH 7.4 drug release rate from the polymer coated tablets was similar in the two compendial media, however in the physiological buffer, they were found to differ in the following order: Eudragit S (aqueous dispersion)>Eudragit FS>Eudragit S (organic solution). The results indicate that the tablets coated with the newer Eudragit FS polymer would be more appropriate for drug delivery to the ileo-colonic region in comparison to the more established Eudragit S. More importantly, however, dissolution in the physiological buffer was found to be markedly slower for all the coated tablets than in the two compendial buffers, a result akin to reported slower dissolution of enteric coated tablets in vivo. There is therefore the need to adequately simulate the ionic composition of the intestinal fluid in the dissolution media.     

Formulation of Solid Dosage Forms to Overcome Gastric pH Interaction of the Factor Xa Inhibitor, BMS-561389

Purpose The purpose of the study was to investigate the specific mechanism by which elevated gastric pH reduces the absorption of BMS-561389, a factor Xa inhibitor, and to develop a solid formulation strategy to overcome this gastric pH interaction. Methods A dissolution method in an acetate buffer at pH 5.5 was used to evaluate the dissolution behavior of the tablet formulation. A precipitation model was used to screen different excipients for their potential to minimize the pH-dependent absorption of BMS-561389. Excipients that showed promise in the precipitation model were incorporated in modified tablet formulations. Dissolution rate of the modified tablets was also determined by the acetate buffer method. A canine model for pH-dependent absorption was subsequently used to evaluate the tablet formulations. Results Dissolution studies suggested that the reduced absorption of the original formulation was the result of the precipitation of the poorly water-soluble free base during the initial dissolution of the salt. Modified tablets containing organic acids, sulfobutylether-β-cyclodextrin, or povidone showed enhanced dissolution as compared with the original formulation. Drug absorption from the tablet containing tartaric acid was substantially independent of gastric pH in the canine model. Conclusion A multitier approach was successful in identifying a solid dosage form that minimizes the pH-dependent absorption of this drug candidate.     

Enhanced solubility and dissolution rate of itraconazole by a solid dispersion technique.

The aim of the present study was to improve the solubility and dissolution rate of a poorly water-soluble drug, itraconazole, by a solid dispersion technique. Solid dispersion particles of itraconazole were prepared with various pH-independent and -dependent hydrophilic polymers and were characterized by differential scanning calorimetry, powder X-ray diffraction and scanning electron microscopy. Of the polymers tested, pH-dependent hydrophilic polymers, AEA and Eudragit E 100, resulted in highest increases in drug solubility (range, 141.4-146.9-fold increases). The shape of the solid dispersion particles was spherical, with their internal diameter ranging from 1-10 microm. The dissolution rate of itraconazole from the tablets prepared by spray drying (SD-T) was fast, with > 90% released within 5 min.SD-T prepared with AEA or Eudragit E 100 at a 1:1 drug hydrophilic polymer ratio (w/w) showed approximately 70-fold increases in the dissolution rate over a marketed product.     

Carvedilol dissolution improvement by preparation of solid dispersions with porous silica

Impregnation of porous SiO(2) (Sylysia) with carvedilol from acetone solution was used to improve dissolution of this poorly water-soluble drug. Solvent evaporation in a vacuum evaporator and adsorption from acetone solution were the methods used to load various amounts of carvedilol into the Sylysia pores. The impregnated carriers were characterized using nitrogen-adsorption experiments, X-ray diffraction, wettability measurements, attenuated total reflectance FTIR spectroscopy and thermal analysis. The impregnation procedures resulted in a significant improvement of drug release compared to dissolution of pure carvedilol or its physical mixtures with Sylysia. The results showed that when the drug precipitated in a thin layer within the carrier the dispersion retained a high specific surface area, micropore volume, and drug-release rate from the solid dispersion. Increasing the amount of drug in the solid dispersion caused particle precipitation within the pores that decreased the carrier's specific surface area and pore volume and decreased the release rate of the drug. The results also suggest that the amorphous form of carvedilol, the improved wettability and weak interactions between the drug and carrier in the solid dispersion also contribute to improved dissolution of the drug from the dispersion.     

New binary solid dispersion of indomethacin with surfactant polymer: From physical characterization to in vitro dissolution enhancement

This article investigated preparation of solid dispersions containing a poor water-soluble drug, indomethacin (IND), and a new surfactant polymer, polyoxyethylene 32 distearate (POED). Solid dispersions were prepared by the melting method and characterized by DSC, hot-stage microscopy (HSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). DSC and HSM analyses performed on IND/POED physical mixtures indicated that IND could dissolve in liquid POED. The materials showed complete miscibility at liquid state. Combination of DSC, XRD, and SEM revealed that these materials had limited miscibility at the solid state. Up to 20% w/w IND in POED, we did not detect significant modification of physical properties of the polymer. It supports the formation of a solid solution of IND in solid POED. Above 20% w/w, the solid dispersions presented particular behavior upon heating (recrystallization of IND) and at the solid state (presence of some IND crystallites). Under 3-month storage at 25°C/53% RH, the solid dispersions demonstrated a good stability of the samples. Finally, in vitro dissolution studies showed that IND release was greatly improved (5.5–12 times as fast) by formation of solid dispersion. This enhancement was principally attributed to the high dispersion of IND in POED and to the polymer surfactant properties. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1399–1413, 2010