无定形固体分散体的溶出与吸收研究进展

无定形固体分散体是提高难溶性药物生物利用度最有效的策略之一,但其易受到处方因素、制备工艺、存储条件和溶出条件等因素的影响从而在储存期或溶出过程中结晶,丧失溶出优势。此外,体内外环境的差异、表观浓度与透膜通量之间的差异、体内吸收过程的复杂性等影响因素使得无定形固体分散体的体外溶出不能完全准确预测体内吸收,给固体分散体产品开发带来了极大挑战。本文总结了关于无定形药物固体分散体溶出与吸收的研究进展,期望为难溶性药物无定形固体分散体制剂的开发提供参考。     

辛伐他汀与阿司匹林共无定形复合物的制备

目的制备辛伐他汀-阿司匹林共无定形复合物,并考察其溶出情况。方法利用溶剂蒸发法制备不同摩尔比的辛伐他汀与阿司匹林样品;采用差示扫描量热分析法(DSC)和粉末X射线衍射法(PXRD)对所制不同摩尔比的辛伐他汀-阿司匹林样品进行表征测定;利用HPLC法对辛伐他汀-阿司匹林共无定形样品进行溶出度测定。结果 DSC和PXRD结果表明,在不同摩尔比的辛伐他汀-阿司匹林样品中,只有摩尔比为2∶1的辛伐他汀-阿司匹林复合物为共无定形药物;溶出测定结果表明,共无定形样品中辛伐他汀的溶出度相对于原料药辛伐他汀有很大提高,但阿司匹林的溶出度没有明显提高。结论辛伐他汀-阿司匹林共无定形复合物的制备,为临床多药联合使用、减少患者用药品种数和提高药物治疗效果提供了新思路和理论基础。     

乳酸环丙沙星温度敏感眼用凝胶的体外释放研究

目的研究乳酸环丙沙星温度敏感眼用凝胶的体外释放规律。方法采用无膜溶出模型考察凝胶溶出规律,采用紫外分光光度法进行药物含量测定。结果乳酸环丙沙星温度敏感眼用凝胶溶蚀和药物释放为零级动力学过程,凝胶溶蚀和药物释放呈良好的线性相关。结论凝胶溶蚀是决定药物释放的主要因素。     

共无定形给药系统研究进展

共无定形药物是将活性药物成分和其他药物或辅料等小分子固体组分混合形成的一种二元单相无定形固体分散体给药系统。作为一种新颖的药物传递系统，共无定形药物可能改善水难溶性药物的溶解度和口服生物利用度问题，为仿制药物和复方药物的开发提供了新的策略和思路。近年来，共无定形药物在学术和制药工业领域受到广泛关注。本文综述了共无定形药物的载体材料的筛选、制备方法、物理稳定机制，以及体外溶出性能和体内吸收情况，并对共无定形药物的未来发展前景进行了展望。     

川陈皮素温敏型鼻用原位凝胶体外释药行为研究

分别采用扩散池法、无膜溶出法以及渗析池法考察川陈皮素温敏型鼻用原位凝胶的体外释药特性与机制.结果表明,川陈皮素原位凝胶通过扩散释放的药物量较少,150 min仅为1.4%;通过无膜溶出法药物释放完全,120 min时药物基本释放完全,且药物的释放量与溶蚀量具有良好的相关性.渗析池法药物的释放量较扩散池法多,120min可释放8%的药物.因此,本实验室研制的川陈皮素温敏型鼻用原位凝胶可能主要通过溶蚀方式释药.     

自微乳化释药系统与液固压缩技术在难溶性中药制剂中的联合应用

药物的难溶性严重影响药物的生物利用度,也严重影响药物制成各类制剂。如何增加中药难溶性成分的溶解度,改善其生物利用度,一直是药剂学研究的重要内容。对于难溶性药物来说,药物只有处于溶解状态下,才能表现出较好的溶出和生物利用度。自微乳化释药系统和液固压缩技术均有很好的增溶作用,而且液固压缩技术使药物以无定形或分子状态给药,两者联合应用,可以显著提高药物的溶出度和生物利用度,为中药增溶领域提供一种新的思路与方法。     

无定形药物固相表征技术的研究进展及应用

无定形药物在提高难溶性药物溶解度、改善其溶出及生物利用度方面具有显著优势,故而广泛应用于药物制剂领域。但无定形药物处于能量较高的非稳态,易发生结晶,从而失去其在溶解度和溶出速率等方面的优势。因此,在无定形药物制剂的制备和储存过程中,为控制质量需要对其进行相应表征。目前,已有包括光学技术、热分析技术、光谱学技术等在内的多种技术被广泛用于无定形药物制剂的研究领域。本文简述无定形药物制剂的多种新发展的表征技术,包括偏光显微镜-控温热台联用、表面光栅衰减、X射线粉末衍射-同步辐射光源技术联用、热分析技术、宽频介电谱、纳米红外光谱分析、拉曼光谱成像、固态核磁共振、荧光分析、X射线光电子能谱等技术,并重点介绍近几年该领域的研究进展及其应用,以期为无定形药物制剂研究和开发提供借鉴。     

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.     

伊曲康唑固体分散体制备及体外溶出实验

目的:运用固体分散体技术提高难溶性药物伊曲康唑的溶解度及体外溶出速率.方法:选用聚乙烯吡咯烷酮(PVPK30)为载体,采用喷雾干燥法制备伊曲康唑固体分散体,通过差热分析及X射线衍射对固体分散体进行鉴定,比较考察伊曲康唑及其物理混合物和固体分散体的溶出特性.结果:差热分析、X射线衍射图谱表明药物以无定形状态分散于载体中;体外溶出结果表明固体分散体能显著增加药物在水及人工胃液中的溶出度(45 min时1:4固体分散体体外溶出度为伊曲康唑的11.5倍.1:4固体分散体在0.1 mo1·L-1盐酸中溶解度是伊曲康唑的67倍).结论:伊曲康唑固体分散体能明显提高伊曲康唑的溶解度及体外溶出速率.     

聚合物辅料对无定形氯雷他定溶出行为和结晶形态的影响

目的 考察聚合物辅料对无定形氯雷他定溶出和结晶的影响。方法 用紫外分光光度法考察无定形氯雷他定在不同体积分数聚维酮K30(PVP-K30)、聚乙二醇4000(PEG 4000)和羟丙基甲基纤维素（hydroxypropyl methylcellulose,HPMC）3种聚合物溶液中的溶出情况;用偏光显微镜观察无定形氯雷他定在水及3种聚合物溶液中的结晶形态及结晶生长情况。结果 不同种类的聚合物对无定形氯雷他定均有一定的增溶作用,聚合物体积分数越高,增溶作用越明显,其中PEG 4000的增溶作用最强。不同种类的聚合物对氯雷他定晶体的生长均有一定的抑制作用。结论 聚合物辅料的种类和体积分数对无定形氯雷他定的溶出特性及晶体形态有一定的影响,为无定形药物稳定性研究及制剂研发提供理论指导。     

Gelation Elimination and Crystallization Inhibition by Co-Amorphous Strategy for Amorphous Curcumin

In the previous study, the development of amorphous curcumin (CUR) aimed to enhance the solubility/dissolution of CUR by disrupting its crystal lattice, but it unexpectedly showed a decreased dissolution than its crystalline counterpart on account of gel formation in its dissolution process. Whether such gelation could be eliminated by co-amorphous strategy was answered in this study. Herein, CUR by co-amorphization with chlorogenic acid (CHA) was successfully prepared using quench cooling. The formed co-amorphous material (namely CUR-CHA CM) eliminated the gelation and hence performed superior dissolution performance than crystalline/amorphous CUR. Meanwhile, it exhibited higher physical stability than amorphous CUR during dissolution as well as under long-term/accelerated conditions. To further study the such enhancement mechanism, the internal molecular interactions were investigated for CUR-CHA CM in the solid state as well as in aqueous solution. FTIR and solid-state ¹³C NMR spectra confirmed that intermolecular hydrogen bonds formed between CUR and CHA after co-amorphization. Furthermore, the nucleation of CUR was significantly inhibited by CHA in an aqueous solution, thus maintaining the supersaturated dissolution for a long time. The present study offers a feasible strategy to eliminate gelation and enhance stability of amorphous solids by co-amorphization and crystallization inhibition.     

Amorphous solid dispersions of carvedilol along with pH‐modifiers improved pharmacokinetic properties under hypochlorhydoria

Carvedilol (CAR) belongs to biopharmaceutics classification system class‐II drugs, with poor aqueous solubility and pH‐dependent solubility. The present study aimed to develop a novel amorphous solid dispersion (ASD) of CAR with acidic counter ions for pH modifications in microenvironment to improve the pharmacokinetic properties under hypochlorhydric conditions. CAR‐ASD was prepared by freeze‐drying in combination with counter ions and hydroxypropyl cellulose, and their physicochemical properties including dissolution behavior, storage stability, and photostability were characterized. Pharmacokinetic studies were carried out after oral administration of CAR samples in both normal and omeprazole‐treated (30 mg/kg, p.o.) rats as a hypochlorhydria model. Among the tested six counter ions, citric acid (CA) was found to be a preferable pH‐modifier of CAR with respect to the dissolution profile and photostability (both potency and colorimetric evaluation). In CAR‐ASD formulation with 50% loading of CA (CAR‐ASD/CA50), amorphization of CAR was observed during the preparation process. After the oral administration of crystalline CAR in rats under hypochlorhydric condition, there was a 34.4% reduction in the systemic exposure of CAR compared with that in normal rats. However, orally‐dosed CAR‐ASD/CA50 resulted in limited alterations of pharmacokinetic behavior between normal and omeprazole‐treated rats. From these findings, addition of CA as pH‐modifier in CAR‐ASD might provide consistent pharmacokinetic behavior of CAR even under hypochlorhydric conditions.     

Enhanced solubility and dissolution of simvastatin by HPMC-based solid dispersions prepared by hot melt extrusion and spray-drying method

The objective of this study was to use low viscosity grade hydroxypropyl methyl cellulose (Methocel^® E3 LV and Methocel^® E5 LV) to enhance the solubility and dissolution of poorly water soluble drug simvastatin (SIM). Two different technologies, hot melt extrusion and spray drying were employed. Characterization of hot melt extrudes and spray dried samples was done by Fourier-transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction studies and scanning electron microscopy. The result of the study showed the conversion of crystalline form drug into amorphous form indicating increase in dissolution rate and solubility of SIM.     

Formulation of highly purified fenugreek gum based silica lipid drug delivery system for simvastatin with enhanced dissolution rate and in vitro characterization

In current study, highly purified fenugreek gum (HPFG) isolated by patented method explored as emulsifier and hydrophilic solid carrier in drug delivery system. Anti-hyperlipidemic drug simvastatin (SIM) was selected as drug model for the study as it is associated with poorly water solubility and low bioavailability problems (<5 %). A suitable HPFG-based silica lipid system composed of SIM (1.5 %), medium chain triglyceride Capmul^® MCM (10 %) as lipid phase, 0.6 % HPFG as emulsifier and HPFG 2.5 %, different grades colloidal silica (7.5 %) (Aerosil^® 300 Pharma, Aerosil^® 380 Pharma and Aeroperl^® 300 Pharma) as hydrophilic solid carriers was developed. The optimized HPFG-based silica lipid systems were characterized for physical characteristics like flow ability, compressibility, redispersiblity, solubility and in vitro drug release using USP apparatus II in pH 6.8 phosphate buffer. The system was also characterized for Fourier transform infrared spectroscopy, powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The developed formulation was found to have excellent flow property, readily redispersiblity, better aqueous solubility and showed 3–4-fold increase in dissolution rate as compared to plain drug and marketed formulation (Simlo^® 10). Transition of crystalline drug to amorphous state was confirmed by DSC, PXRD and SEM studies. Enhanced dissolution rate and solubility possibly attributed to improved wetting, amorphous drug state and facilitated diffusion from lipid-based system. Thus developed HPFG-based silica lipid system provides an alternative means for SIM with enhanced dissolution rate and stability in oral solid dosage form.     

Effect of wet milling process on the solid state of indomethacin and simvastatin

The aim of this study was to investigate the effect of wet milling on the solid state of indomethacin (IMC) and simvastatin (SIM). Wet milling was performed using high pressure homogenization (HPH). Polyvinylpyrrolidone-K25 (PVP) and poloxamer 407 (P407) were used as suspension stabilizers. Samples were characterized before and after wet milling using particle size analyzer, scanning electron microscopy (SEM), infrared (IR) spectroscopy and modulated temperature differential scanning calorimetry (MTDSC) techniques. After wet milling of IMC, physical appearance and IR spectra indicated surface amorphization; however, the solid state of SIM remained unaffected. MTDSC could not detect surface amorphization in IMC, suggesting that if present, it was only at very low levels. These results are in contradiction to the previous reports where dry milling of IMC and SIM resulted in amorphization of crystalline particles. Moreover, cryogrinding of IMC in the absence of water resulted in an amorphous form while presence of water using the same cryogrinding conditions resulted in a solid state similar to that obtained after wet milling. These results signify the role of water in inhibiting the amorphization during wet milling of crystalline drugs.     

Physical characterization of solid iopanoic acid forms.

Three solid forms of iopanoic acid were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, thermal microscopy, IR spectroscopy, and dissolution studies. X-ray analysis demonstrated that two solid forms were crystalline and that the third was amorphous. The amorphous form had been reported previously as crystalline. Enthalpies and entropies of transition were calculated using differential scanning calorimetry. A fourth form, a benzene solvate, also was isolated but proved to be too unstable at room temperature to permit conclusive characterization. The amorphous form demonstrated a 10-fold greater intrinsic dissolution rate than the commercially available form (Form I). Form II's intrinsic dissolution rate was 1.5 times greater than that of Form I. In powder dissolution studies, the peak solubilities of the different forms followed the same rank order as their intrinsic dissolution rates. Form II was relatively stable in aqueous saturated solutions, but the amorphous form was rapidly converted to Form I under similar conditions.     

Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizers

The purpose of this study was to obtain an amorphous system with minimum unit operations that will prevent recrystallization of amorphous drugs since preparation, during processing (compression) and further storage. Amorphous celecoxib, solid dispersion (SD) of celecoxib with polyvinyl pyrrollidone (PVP) and co-precipitate with PVP and carrageenan (CAR) in different ratios were prepared by the spray drying technique and compressed into tablets. Saturation solubility and dissolution studies were performed to differentiate performance after processing. Differential scanning calorimetry and X-ray powder difraction revealed the amorphous form of celecoxib, whereas infrared spectroscopy revealed hydrogen bonding between celecoxib and PVP. The dissolution profile of the solid dispersion and co-precipitate improved compared to celecoxib and amorphous celecoxib. Amorphous celecoxib was not stable on storage whereas the solid dispersion and co-precipitate powders were stable for 3 months. Tablets of the solid dispersion of celecoxib with PVP and physical mixture with PVP and carrageenan showed better resistance to recrystallization than amorphous celecoxib during compression but recrystallized on storage. However, tablets of co-precipitate with PVP and carageenan showed no evidence of crystallinity during stability studies with comparable dissolution profiles. This extraordinary stability of spray-dried co-precipitate tablets may be attributed to the cushioning action provided by the viscoelastic polymer CAR and hydrogen bonding interaction between celecoxib and PVP. The present study demonstrates the synergistic effect of combining two types of stabilizers, PVP and CAR, on the stability of amorphous drug during compression and storage as compared to their effect when used alone.     

Plasticized Drug‐Loaded Melt Electrospun Polymer Mats: Characterization,Thermal Degradation,and Release Kinetics

Melt electrospinning (MES) was used to prepare fast dissolving fibrous drug delivery systems in the presence of plasticizers. This new method was found promising in the field of pharmaceutical formulation because it combines the advantages of melt extrusion and solvent‐based electrospinning. Lowering of the process temperature was performed using plasticizers in order to avoid undesired thermal degradation. Carvedilol (CAR), a poorly water‐soluble and thermal‐sensitive model drug, was introduced into an amorphous methacrylate terpolymer matrix, Eudragit® E, suitable for fiber formation. Three plasticizers (triacetin, Tween® 80, and polyethylene glycol 1500) were tested, all of which lowered the process temperature effectively. Scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, and Raman microspectrometry investigations showed that crystalline CAR turned into an amorphous form during processing and preserved it for longer time. In vitro dissolution studies revealed ultrafast drug dissolution of the fibrous samples. According to the HPLC impurity tests, the reduced stability of CAR under conditions applied without plasticizer could be avoided using plasticizers, whereas storage tests also indicated the importance of optimizing the process parameters during MES. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1278–1287, 2014     

Solid molecular dispersions of poorly water-soluble drugs in poly(2-hydroxyethyl methacrylate) hydrogels.

The applicability of cross-linked hydrogels in forming solid molecular dispersions to enhance the delivery of poorly soluble drugs has not been fully explored. The purpose of this study is to characterize physicochemical parameters affecting the formation of solid molecular dispersions of poorly water-soluble drugs in poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels and to investigate the effect of storage humidity levels on their physical stability. Samples were prepared by an equilibrium solvent loading process, using diclofenac sodium, piroxicam and naproxen as model drugs. These were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), as well as changes in the physical state during storage under different humidity conditions. The results show that a threshold drug loading level of about 30% exists in these solid molecular dispersions, above which amorphous to crystalline transition may occur. At any given drug loading, the onset of such change in physical state is accelerated at higher relative humidity levels during storage. The presence of hydrogen bonding between the polymer and the drug, as reflected in the observed FTIR band shifts, improves the compatibility between the drug and the polymer. This, together with a decreased mobility in the glassy polymer, helps to retard the crystallization event below the loading threshold. An increase in dissolution rate is also observed from the polymeric solid molecular dispersion as compared with that of the crystalline pure drug. These physicochemical results indicate that solid molecular dispersions based on PHEMA hydrogels can effectively enhance the dissolution and therefore should be potentially useful in improving the oral bioavailability of poorly water-soluble drugs.     

Stable and Fast-Dissolving Amorphous Drug Composites Preparation via Impregnation of Neusilin® UFL2

A promising approach to increase the aqueous solubility, hence the bioavailability, of poorly water-soluble drugs is to convert them into their amorphous state through impregnation into mesoporous silica. Unfortunately, mesoporous silica is not yet available in bulk quantities due to high manufacturing costs. In this work, feasibility of using a commercially available cost-effective mesoporous fine grade Neusilin^® UFL2 to prepare amorphous drug composites of 2 model poorly soluble drugs, fenofibrate and itraconazole, is established. In contrast to fluidized-bed spray-impregnation, only mixing and drying steps are required. Complimentary assessment using X-ray powder diffraction, differential scanning calorimetry, and Raman spectroscopy confirmed drug within the composites to be amorphous at as high as 30% drug loading both after formation and after 3 months of storage at 40°C and 75% relative humidity. Amorphous drug recrystallization was completely suppressed due to the confinement effect due to the Neusilin^®. The amorphous drug composites resulted in higher apparent solubility and faster dissolution rate of the model drugs as compared to their crystalline counterpart, confirmed by United States Pharmacopeia II dissolution and ultraviolet surface dissolution imaging. Overall, stable, high drug-loaded fast-dissolving amorphous drug composites preparation using Neusilin^® UFL2 is demonstrated as a promising approach to enhance solubility of poorly soluble drugs.