Effects of Molecular Interactions on Miscibility and Mobility of Ibuprofen in Amorphous Solid Dispersions With Various Polymers

Hydrogen bonds (HBs) in amorphous solid dispersions may influence physical stability through effects on both drug miscibility and mobility. Amorphous solid dispersions containing the HB-donor ibuprofen (IBP) alone or with one of four model polymers (poly(vinyl pyrrolidone) [PVP], poly(vinyl pyrrolidone/vinyl acetate) [PVP/VA], poly(vinyl acetate) [PVA], or polystyrene [PST]) were monitored by molecular dynamics simulation. HB distributions and contributions of electrostatic, van der Waals, and internal interactions to miscibility and mobility were analyzed versus drug concentration. The probability of IBP-IBP HBs decreases markedly (0.6→0.0) with dilution (100→10% drug) in PVP due to IBP-PVP HBs while dilution in the nonpolar PST has a more modest effect on IBP-IBP HB probability (0.6→0.3). Concentration-dependent Flory-Huggins interaction parameters (χ) were determined to assess drug-polymer miscibility. χ_IBP-PVP values were ?0.9 to ?1.8 with a plateau near 50% w/w PVP, whereas χ_IBP-PST fluctuated near zero (?0.1 to 0.3), suggesting that IBP is more soluble in PVP than in PST. χ_IBP-polymer values in polymers varying in pyrrolidone/acetate composition were in the order PVP (most favorable) > PVP/VA > PVA (least favorable). Decreased local mobility of IBP measured by the atomic fluctuation correlates with more IBP-PVP HBs with increasing PVP content. The opposite trend in IBP-PST may arise from IBP-IBP HB disruption on dilution.     

尼莫地平固体分散物的研究

尼莫地平临床上主要用于防治缺血性脑血管疾病．该药为难溶性药物，生物利用度低，本文采用了固体分散技术制备了尼莫地平两种固体分散物，其体外溶出速率１０分钟以内达８０％以上，较市售片有显著提高．两种固体分散物中，固体分散物Ⅰ为本实验室研制，固体分散物Ⅱ参照国内、外文献用ＰＶＰ为载体制备．两种固体分散物均能明显提高尼莫地平的体外溶出速率，但固体分散物Ⅱ易于老化，经相对湿度ＲＨ７５％４０℃贮藏３个月溶出速率明显下降，同样条件下，固体分散物Ⅰ则无明显变化．二种固体分散物Ｘ－射线衍射图谱表明尼莫地平以非晶体状态存在，而在ＲＨ７５％４０℃条件下放置３个月后，固体分散物ⅡＸ－射线衍射图谱出现了尼莫地平结晶峰．     

Producing Amorphous Solid Dispersions via Co-Precipitation and Spray Drying: Impact to Physicochemical and Biopharmaceutical Properties

Many small-molecule active pharmaceutical ingredients (APIs) exhibit low aqueous solubility and benefit from generation of amorphous dispersions of the API and polymer to improve their dissolution properties. Spray drying and hot-melt extrusion are 2 common methods to produce these dispersions; however, for some systems, these approaches may not be optimal, and it would be beneficial to have an alternative route. Herein, amorphous solid dispersions of compound A, a low-solubility weak acid, and copovidone were made by conventional spray drying and co-precipitation. The physicochemical properties of the 2 materials were assessed via X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, and scanning electron microscopy. The amorphous dispersions were then formulated and tableted, and the performance was assessed in vivo and in vitro. In human dissolution studies, the co-precipitation tablets had slightly slower dissolution than the spray-dried dispersion, but both reached full release of compound A. In canine in vitro dissolution studies, the tablets showed comparable dissolution profiles. Finally, canine pharmacokinetic studies showed that the materials had comparable values for the area under the curve, bioavailability, and C_max. Based on the summarized data, we conclude that for some APIs, co-precipitation is a viable alternative to spray drying to make solid amorphous dispersions while maintaining desirable physicochemical and biopharmaceutical characteristics.     

尼群地平固体分散体体外溶出度研究

目的:选择尼群地平固体分散体适宜的体外溶出介质。方法:测定尼群地平在多种溶出介质中的溶解度，通过体外溶出度试验比较尼群地平固体分散体在不同溶出介质中的溶出行为。结果:溶出介质1.0%和0.5%的十二烷基硫酸钠(SDS)水溶液可以满足“漏槽”条件，但药物释放较快，固体分散体间的溶出行为差异不明显；0.3%的SDS水溶液可以保证药物的全部溶出，且可以明显区别各固体分散体之间的溶出差异。结论:选用0.3%的SDS水溶液作为溶出介质，便于通过溶出度试验来筛选固体分散体处方。     

冬凌草甲素固体分散体的制备及溶解性能研究

目的 采用固体分散技术,提高冬凌草甲素的体外溶解性能。方法 分别以聚乙二醇6000(PEG6000)、聚乙烯吡咯烷酮K30(PVPK30)为载体,制备冬凌草甲素固体分散体。采用紫外分光光度法进行含量测定,差示热分析法鉴别药物在载体中的存在状态,并进行溶解度、体外溶出速率实验。结果 两种载体的固体分散体均能增加药物的溶解度和溶出速率,冬凌草甲素在载体中以高度分散状态存在。结论 以 PVPK30为载体制备的冬凌草甲素固体分散体体外溶解度和溶出速率明显提高。     

Spectroscopic Characterization of Interactions Between PVP and Indomethacin in Amorphous Molecular Dispersions

Purpose. To study the molecular structure of indomethacin-PVP amorphous solid dispersions and identify any specific interactions between the components using vibrational spectroscopy. Methods. Solid dispersions of PVP and indomethacin were prepared using a solvent evaporation technique and IR and FT-Raman spectra were obtained. Results. A comparison of the carbonyl stretching region of indomethacin, known to form carboxylic acid dimers, with that of amorphous indomethacin indicated that the amorphous phase exists predominantly as dimers. The hydrogen bonding of indomethacin is not as dimers. Addition of PVP to amorphous indomethacin increased the intensity of the infrared band assigned to non-hydrogen bonded carbonyl. Con-comitantly, the PVP carbonyl stretch appeared at a lower wavenumber indicating hydrogen bonding. Model solvent systems aided spectral interpretation. The magnitude of the spectral changes were comparable for an indomethacin-PVP solid dispersion and a solution of indomethacin in methylpyrrolidone at the same weight percent. Conclusions. Indomethacin interacts with PVP in solid dispersions through hydrogen bonds formed between the drug hydroxyl and polymer carbonyl resulting in disruption of indomethacin dimers. PVP may influence the crystallisation kinetics by preventing the self association of indomethacin molecules. The similarity of results for solid dispersions and solutions emphasises the 'solution' nature of this binary amorphous state.     

Influence of Glass Forming Ability on the Physical Stability of Supersaturated Amorphous Solid Dispersions

In this study, the influence of the glass-forming ability (GFA) of a drug on its physical stability in a supersaturated solid dispersion was investigated. Nine drugs were classified according to their GFA using their respective critical cooling rate. Their respective solubility in poly(vinylpyrrolidone-co-vinyl acetate) 6:4 (PVPVA64) was predicted using the melting point depression method based on the Flory-Huggins lattice theory. Supersaturated amorphous solid dispersions at a level of 25% w/w drug above saturation solubility in the polymer were prepared by film-casting, and their respective physical stability at temperatures of 10°C or 20°C above or below their respective T_g (dry conditions) was monitored by the use of polarized light microscopy. This study showed that drugs with good GFA (class 3) on average have higher physical stability in supersaturated amorphous solid dispersion compared to drug with modest GFA (class 2), which in turn have higher physical stability in supersaturated amorphous solid dispersion than drugs with poor GFA (class 1). These results indicate that the GFA of a drug and its physical stability in a supersaturated amorphous solid dispersion stored at a temperature above or below its T_g are correlated.     

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.     

Physical Stability and Dissolution of Lumefantrine Amorphous Solid Dispersions Produced by Spray Anti-Solvent Precipitation

This study aims to develop amorphous solid dispersion (ASD) of lumefantrine with a cost-effective approach of spray anti-solvent precipitation. Four acidic polymers, hydroxypropylmethylcellulose phthalate (HPMCP), hydroxypropylmethylcellulose acetate succinate (HPMCAS), poly(methacrylic acid–ethyl acrylate) (EL100) and cellulose acetate phthalate (CAP) were studied as excipients at various drug-polymer ratios. Of the studied polymers, satisfactory physical stability was demonstrated for HPMCP- and HPMCAS-based ASDs with no observed powder X-ray diffraction peaks for up to 3 months of storage at 40 °C/75% RH. HPMCP and HPMCAS ASDs also achieved greater drug release levels in the dissolution study than other polymers. The HPMCP-based ASDs with a drug:polymer ratio of 2:8 exhibited a maximum drug release of 140 μg/mL for up to 2 h, which is significantly higher than the currently marketed formulation of Coartem® (<80 ng/mL). Relatively, the CAP and EL100 ASDs indicated a higher water content and crystallized within a day when stored at 40 °C/75% RH. The choice of polymer, and the drug-polymer ratio played a crucial role in the solubility enhancement of lumefantrine. Our study indicates that the developed spray anti-solvent precipitation method could be an affordable approach for producing ASDs.     

Mechanical Properties and Tableting Behavior of Amorphous Solid Dispersions

Amorphous solid dispersions (ASDs) consisting of acetaminophen (APAP) and copovidone were systematically studied to identify effects of drug loading and moisture content on mechanical properties, thermal properties, and tableting behavior. ASDs containing APAP at different levels were prepared by film casting and characterized by differential scanning calorimetry and nanoindentation. The glass transition temperature (T_g) continuously decreased with increasing amount of APAP, but the hardness of ASDs was increased at a low APAP content and reduced at high APAP content. This in turn significantly influenced tablet quality. Water reduced both the hardness and T_g of ASDs, and the APAP loading level corresponding to the transition to the softening mechanism was lower at a higher relative humidity. Overall, the mechanical properties, rather than the thermal properties, better represent the plasticization/antiplasticization effect of small molecule to ASDs.     

坎地沙坦固体分散体的制备及溶出度、稳定性研究

目的利用固体分散技术提高坎地沙坦的溶解性。方法以体外溶出度为指标,通过单因素试验,考察处方和工艺因素对坎地沙坦固体分散体中药物溶出的影响,运用正交试验选定坎地沙坦固体分散体的最优处方;采用FTIR、DSC、XRD分析技术对药物与载体间的相互作用及药物在固体分散体中的存在状态进行鉴定,探讨固体分散体的增溶机制,考察固体分散体的稳定性。结果以聚乙烯吡咯烷酮（PVPK30）为载体,二氯甲烷：甲醇：乙醇－2：2：l为混合溶剂制备的固体分散体溶出度lh可达99％;红外分析表明坎地沙坦与PVPK30间有氢键形成;DSC及XRD表征表明坎地沙坦以微晶或无定形态分散于PVPK30中;稳定性加速试验显示固体分散体经过30d后XRD显示药物无明显的团聚,仍以微晶或无定形态存在。结论固体分散技术能有效提高坎地沙坦的溶出度。制得的坎地沙坦固体分散体为一稳定体系,具有实际应用价值。     

Characterization and Physical Stability of Spray Dried Solid Dispersions of Probucol and PVP-K30

The main purpose of this study was to obtain stable, well-characterized solid dispersions (SDs) of amorphous probucol and polyvinylpyrrolidone K-30 (PVP-K30) with improved dissolution rates. A secondary aim was to investigate the flow-through dissolution method for in-vitro dissolution measurements of small-sized amorphous powders dispersed in a hydrophilic polymer. SDs were prepared by spray drying solutions of probucol and different amounts of PVP-K30. The obtained SDs were characterized by dissolution rate measurements in a flow-through apparatus, X-ray Powder Diffraction (XRPD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), particle sizing (laser diffraction) and Brunauer-Emmett-Teller Method (BET) and results were compared with starting material and a physical mixture. The physical stability was monitored after storage at 25°C and 60% RH for up to 12 weeks. The flow-through method was found suitable as dissolution method. All SDs showed improved in-vitro dissolution rates when compared to starting material and physical mixtures. The greatest improvement in the in-vitro dissolution rate was observed for the highest polymer to drug ratio. By means of the results from XRPD and DSC, it was argued that the presence of amorphous probucol improved the dissolution rate, but the amorphous state could not fully account for the difference in dissolution profiles between the SDs. It was suggested that the increase in surface area due to the reduction in particle size contributed to an increased dissolution rate as well as the presence of PVP-K30 by preventing aggregation and drug re-crystallization and by improving wettability during dissolution. The stabilizing effect of the polymer was verified in the solid state, as all the SDs retained probucol in the amorphous state throughout the entire length of the stability study.     

三维有序大孔壳聚糖/尼莫地平固体分散体的研究

目的制备孔径为470nm的三雏有序大孔壳聚糖／尼莫地平的固体分散体,研究其释药特点、稳定性和药动学。方法利用溶剂蒸发法制备固体分散体,通过药物释放试验考察固体分散体在模拟胃肠液介质中的释放行为;通过含量测定、X-射线衍射和溶出试验检查固体分散体的稳定性;大鼠分别给予自制固体分散体和市售片粉末,测定血药浓度。结果固体分散体在pH6.8的介质中的溶出度明显比pH1.2和pH4.5介质中高,在梯度pH介质中的释药曲线类似阶梯型;结晶度和溶出度在考察时间内基本无变化;自制固体分散体的AUC0.12h是市售制剂的1.91倍,具有长效作用。结论自制固体分散体稳定性良好,能够提高尼莫地平的大鼠口服生物利用度。     

Non-Sink Dissolution Behavior and Solubility Limit of Commercial Tacrolimus Amorphous Formulations

An increasing number of drugs with low aqueous solubility are being formulated and marketed as amorphous solid dispersions because the amorphous form can generate a higher solubility compared to the crystalline solid. The amorphous solubility of a drug can be determined experimentally using various techniques. Most studies in this area investigate the drug in its pure form and do not evaluate any effects from other formulation ingredients. In this study, we use 6 marketed amorphous oral drug products, capsules containing 5 mg of tacrolimus, and various excipients, consisting of 1 innovator product and 5 generics. The amorphous solubility of tacrolimus was evaluated using different techniques and was compared to the crystalline solubility of the drug. Dissolution of the different products was conducted under non-sink conditions to compare the maximum achieved concentration with the amorphous solubility. Diffusion studies were performed to elucidate the maximum flux across a membrane and to evaluate whether there was any difference in the thermodynamic activity of the drug released from the formulation and the pure drug. The amorphous solubility of tacrolimus was found to be a factor of 35 higher than the crystalline solubility. The maximum concentration obtained after dissolution of the capsule contents in non-sink conditions was found to match the experimentally determined amorphous solubility of the pure drug. Furthermore, the membrane flux of tacrolimus following dissolution of the various formulations was found to be similar and maximized. This study demonstrates a link between key physicochemical properties (amorphous solubility) and in vitro formulation performance.     

Phase Behavior of Amorphous Molecular Dispersions II: Role of Hydrogen Bonding in Solid Solubility and Phase Separation Kinetics

No HeadingPurpose. To determine the factors influencing solid solubility and phase separation kinetics of drugs from amorphous solid dispersions.Methods. Solid dispersions of griseofulvin-poly(vinyl pyrrolidone) (PVP) and indoprofen-PVP were prepared using solvent evaporation technique. Dispersions demonstrating single T_g were exposed to 40°C/69% RH for 90 days. Drug solid solubility in the polymer and phase separation rates were determined from changes in T_g of solid dispersions. FTIR spectroscopy and XRD were used to characterize drug-polymer interactions and drug crystallinity, respectively.Results. Freshly prepared solid dispersion of up to 30% w/w griseofulvin and indoprofen were molecularly miscible with PVP. Hydrogen bonding was evident in indoprofen-PVP, but not in griseofulvin-PVP dispersions. When exposed to 40°C/69% RH, griseofulvin phase separated completely, whereas the solid solubility of indoprofen was determined as 13% w/w. The first-order rate constants of phase separation for 10%. 20%, and 30% w/w griseofulvin dispersions were estimated as 4.66, 5.19, and 12.50 (×10²) [day^–1], and those of 20% and 30% w/w indoprofen were 0.62 and 1.25 (×10²) [day^–1], respectively.Conclusions. Solid solubility of griseofulvin and indoprofen in PVP is 0% w/w and 13% w/w, respectively. Drug-polymer hydrogen bonding in indoprofen-PVP dispersions favors solid solubility. Phase separation rate of drug from the solid dispersions depends on the initial drug content and the nature of drug-polymer interactions.     

Correlationship of Drug-Polymer Miscibility,Molecular Relaxation and Phase Behavior of Dipyridamole Amorphous Solid Dispersions

In present work, a correlationship among quantitative drug-polymer miscibility, molecular relaxation and phase behavior of the dipyridamole (DPD) amorphous solid dispersions (ASDs), prepared with co-povidone (CP), hydroxypropyl methylcellulose phthalate (HPMC P) and hydroxypropyl methylcellulose acetate succinate (HPMC AS) has been investigated. Miscibility predicted using melting point depression approach for DPD with CP, HPMC P and HPMC AS at 25 °C was 0.93% w/w, 0.55% w/w and 0.40% w/w, respectively. Stretched relaxation time (τ^β) for DPD ASDs, measured using modulated differential scanning calorimetry (MDSC) at common degree of undercooling, was in the order of DPD- CP > DPD-HPMC P > DPD-HPMC AS ASDs. Phase behavior of 12 months aged (25 ± 5 °C and 0% RH) spray dried 60% w/w ASDs was tracked using MDSC. Initial ASD samples had homogeneous phase revealed by single glass transition temperature (T_g) in the MDSC. MDSC study of aged ASDs revealed single-phase DPD-CP ASD, amorphous-amorphous and amorphous-crystalline phase separated DPD-HPMC P and DPD-HPMC AS ASDs, respectively. The results were supported by X-ray micro computed tomography and confocal laser scanning microscopy studies. This study demonstrated a profound influence of drug-polymer miscibility on molecular mobility and phase behavior of ASDs. This knowledge can help in designing “physical stable” ASDs.     

Characterization and Physical Stability of Tolfenamic Acid-PVP K30 Solid Dispersions

Obtaining a stable formulation with high bioavailability of a poorly water-soluble drug often presents a challenge to the formulation scientist. Transformation of the drug into its more soluble high-energy amorphous form is one method used for improving the dissolution rate of such compounds. The present study uses the spray-drying technique for preparation of solid dispersions (SDs) of tolfenamic acid (TA) and polyvinylpyrrolidone K-30 (PVP). The SDs and TA in the form of a spray-dried powder were initially characterized and compared with a physical mixture and starting materials. Stability of the SDs was monitored over 12 weeks at 25°C and 60% RH. XRPD studies revealed changes in solid state during the formation of the SDs and indicated the presence of TA in the amorphous state. FTIR, together with TGA, suggested molecular interactions (hydrogen-bonding) in the SDs. Dissolution studies proved an increase in the dissolution rate of TA from all SDs. The SDs with higher content of PVP retained TA in the amorphous state throughout the stability study. However, SDs with lower content showed recrystallization of TA after 1 week. Thus, this study reveals the possibility of preparing stable SDs of amorphous TA in PVP with improved dissolution rate.     

Effect of Particle Size and Polymer Loading on Dissolution Behavior of Amorphous Griseofulvin Powder

The effect of particle size on the dissolution behavior of the particles of amorphous solid dispersions (ASDs) of griseofulvin (GF), with 0%-50% Kollidon^® VA 64 as a crystallization inhibitor is investigated. Both the final dissolved GF concentration and the dissolution rate of GF ASDs were found to be inversely proportional to the particle size. The solution concentrations for the smallest (45-75 μm) size group with different polymer loadings were significantly higher than those for the largest (250-355 μm) group regardless of the initial GF amount. Specifically, the dissolution rate of GF ASDs with 50% polymer loading for the finest group was 2.7 times higher than for the largest group under supersaturating conditions. The rates of dissolution and recrystallization were assessed through surface concentration (C_s) and Avrami recrystallization rate kinetics, where the solid-state recrystallization was confirmed using Raman spectroscopy. Outcomes indicated that particle size reduction enhanced ASD drug loading by reducing the amount of polymer necessary as finest size ASDs initially dissolve faster, negating their higher recrystallization rate. Kollidon® VA 64 at 30% loading was sufficient to inhibit the GF recrystallization. Overall, the combination of particle size reduction and recrystallization inhibition is effective for improved dissolution behavior of GF ASDs.     

Investigation of Ethylene Oxide-co-propylene Oxide for Dissolution Enhancement of Hot-Melt Extruded Solid Dispersions

The optimal design of amorphous solid dispersion formulations requires the use of excipients to maintain supersaturation and improve physical stability to ensure shelf-life stability and better absorption during intestinal transit, respectively. Blends of excipients (surfactants and polymers) are often used within pharmaceutical products to improve the oral delivery of Biopharmaceutical Classification System class II drugs. Therefore, in this study, a dissolution enhancer, poloxamer 407 (P407), was investigated to determine its effect on the dissolution properties and on the amorphous nature of the active pharmaceutical ingredient contained in the formulation. Phase solubility studies of indomethacin (INM) in aqueous solutions of P407 and poly(vinylpyrrolidone-vinyl acetate copolymer) showed an increase in the kinetic solubility of INM compared with the pure drug at 37°C with a K_a value of 0.041 μg/mL. The solid dispersions showed a higher dissolution rate when compared to pure and amorphous drugs when performed in pH buffer 1.2 with a kinetic solubility of 21 μg/mL. The stability data showed that the amorphous drug in solid solutions with poly(vinylpyrrolidone-vinyl acetate copolymer) and P407 remained amorphous, and the %P407 loading had no effect on the amorphous stability of INM. This study concluded that the amorphous solid dispersion contributed to the increased solubility of INM.     

白藜芦醇-壳寡糖无定型固体分散体的制备与体外评价

目的 将白藜芦醇（resveratrol,RES）和壳寡糖（chitosan oligosaccharide,COS）联合使用制备成白藜芦醇无定型固体分散体（RES-COS amorphous solid dispersion,RES-COS ASD）,提高RES的体外溶出度。方法 通过球磨法制备RES-COS ASD,采用差示扫描量热分析、粉末X-射线衍射、扫描电镜和傅里叶红外光谱对制备的RES-COS ASD进行表征分析,对RES-COS ASD在漏槽和非漏槽条件下的体外溶出进行评价,并考察RES-COS ASD的物理稳定性。结果 差示扫描量热分析、粉末X-射线衍射结果表明,RES-COS ASD制备成功。扫描电镜观察发现该无定型固体分散体呈不规则块状、颗粒状,RES和COS的特征不可见。在RES-COS ASD （1∶4）、RES-COS ASD （1∶2）中,RES的饱和溶解度显著提高（P<0.01）,分别为晶体RES原料药的2.37倍和2.29倍。漏槽条件下（20 min时）,与RES原料药组相比,RES-COS ASD组中RES的累积溶出率显著提高（P<0.01）。非漏槽条件下体外溶出结果表明,与RES原料药相比,RES-COS ASD组中RES具有较高的体外溶出度,并且维持长时间的超饱和程度。另外,RES-COS ASD在25℃和40℃条件下,至少保持6个月的物理稳定性。结论 RES和COS联合使用制备的RES-COS ASD能够有效地改善RES的体外溶出度以及维持超饱和程度。