Enhancement of bioavailability and anthelmintic efficacy of albendazole by solid dispersion and cyclodextrin complexation techniques

The objective of this study was to improve the oral bioavailability and therapeutic efficacy of albendazole (ABZ) employing solid dispersion and cyclodextrin complexation techniques. Solid dispersion (dispersion) was prepared using ABZ and polyvinylpyrrolidone (PVP) polymer (1:1 weight ratio). Ternary inclusion complex (ternary complex) was prepared using ABZ, hydroxypropyl beta-cyclodextrin (HPbetaCD) and L-tartaric acid (1:1:1 molar ratio). In rabbits with high gastric acidity (gastric pH approximately 1), ternary complex and solid dispersion showed a bioavailability enhancement of 3.2 and 2.4 fold respectively, compared to a commercial suspension (p < 0.05). The rise in gastric pH (pH > 5) caused a 62% reduction in AUC (area under the plasma level curve) for the commercial suspension, whereas the reduction in case of PVP dispersion and ternary complex was only 43% and 37% respectively. The rapid absorption of the drug from solid dispersion and ternary complex was reflected in improved anthelmintic efficacy against the systemic phases of Trichinella spiralis. The ternary complex was significantly more efficient than solid dispersion and exhibited the highest larvicidal activity (90%) at a dose of 50 mg x kg(-1) (p < 0.05). These results suggest that the bioavailability and therapeutic efficacy of the ternary complex might be high even if there is a great variation in the gastric pH.     

Development of raloxifene-solid dispersion with improved oral bioavailability via spray-drying technique

The purpose of this study was to develop a raloxifene-loaded solid dispersion with enhanced dissolution rate and bioavailability via spray-drying technique. Solid dispersions of raloxifene (RXF) were prepared with PVP K30 at weight ratios of 1:4, 1:6 and 1:8 using a spray-drying method, and characterized by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and solubility and dissolution tests. The bioavailability of the solid dispersion in rats was also evaluated compared to those of RXF powder and commercial product. Results showed that the RXF-loaded solid dispersion was in amorphous form with increased solubility and dissolution rate. The absorption of RXF from solid dispersion resulted in approximately 2.6-fold enhanced bioavailability compared to pure drug. Moreover, RXF-loaded solid dispersion gave similar AUC, C_max and T_max values to the commercial product, suggesting that it was bioequivalent to the commercial product in rats. These findings suggest that an amorphous solid dispersion of RXF could be a viable option for enhancing the oral bioavailability of RXF.     

Novel crystalline solid dispersion of tranilast with high photostability and improved oral bioavailability

Tranilast (TL) is an anti-allergic agent and widely used in the clinical treatment of bronchial asthma, atopic rhinitis, atopic dermatitis and keloids. However, therapeutic potential of TL could be partly limited because of its poor solubility, bioavailability, and photostability. To overcome these drawbacks, crystalline solid dispersion of TL (CSD/TL) was prepared by wet-milling technique with aim of improving physicochemical and pharmacokinetic properties. Physicochemical properties of the formulations prepared were characterized by laser diffraction and dynamic light scattering for particle size analysis, scanning electron microscope for morphological analysis, and powder X-ray diffraction and differential scanning calorimetry for crystallinity assessment. TL particles in CSD/TL appeared to be crystalline with diameter of 122 nm, and CSD/TL exhibited marked improvement in the dissolution behavior as compared to crystalline TL. Under irradiation of UVA/B (250 W/m²), solution and amorphous solid dispersion of TL were found to be highly photodegradable, whereas high photochemical stability was seen in CSD/TL. After oral administration of CSD/TL, enhanced TL exposure was observed with increase of C_max and AUC by 60- and 32-fold, respectively, as compared to crystalline TL. According to these observations, taken together with dissolution and pharmacokinetic behaviors, crystalline solid dispersion strategy would be efficacious to enhance bioavailability of TL with high photochemical stability.     

Improving the dissolution and oral bioavailability of the poorly water‐soluble drug aloe‐emodin by solid dispersion with polyethylene glycol 6000

Solid dispersions (SDs) of aloe‐emodin (AE) and polyethylene glycol 6000 (PEG6000) with different drug loadings were prepared, characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) and evaluated for solubility and in vitro release. The oral bioavailability of AE from SD in rats was compared with the crystalline drug. Plasma concentrations of AE were determined by HPLC. After administration of crystalline AE (35 mg·kg^?1) in rats, the AUC_0‐600 and C_max were 393.6±77.1 mg·min·l^?1 and 1.87±0.30 mg·l^?1, respectively. For the PEG6000 SD of AE, AUC_0‐600 and C_max were boosted to 1310.5±111.9 mg·min·l^?1 and 5.86±0.47 mg·l^?1, respectively. The results indicated that the oral bioavailability of AE was increased significantly. Simultaneously, the T_max value of AE for AE crystalline was decreased from 75.6±17.3 min to 44.8±14.8 min for SD. The earlier T_max for AE from SD indicated the higher extent of absorption for SD due to their improved dissolution rate in rat intestine. This SD approach can therefore be used to enhanced dissolution and bioavailability for poorly water‐soluble drugs. Drug Dev Res, 2009. © 2009 Wiley‐Liss, Inc.     

A novel solid dispersion system for natural product-loaded medicine: silymarin-loaded solid dispersion with enhanced oral bioavailability and hepatoprotective activity

Abstract

A surface-attached silymarin-loaded solid dispersion with improved dissolution profile and enhanced oral bioavailability was formulated using silymarin, polyvinylpyrrolidone (PVP) and Tween 80 in water. In this solid dispersion, hydrophilic PVP was adhered onto the surface of crystalline drug rendering silymarin hydrophilic without changing its crystallinity. The drug solubility from the optimised solid dispersion prepared with silymarin/PVP/Tween 80 at the weight ratio of 5/2.5/2.5 increased by almost 650-fold compared to drug powder. The drug was physically and chemically stable in the solid dispersion for at least 6 months. Moreover, the solid dispersion enhanced the oral bioavailability of the drug in rats by almost 3-fold compared to the commercial product. The silymarin-loaded solid dispersion also exhibited advanced hepatoprotective bioactivity against CCl₄-induced liver damage compared to silymarin or the commercial product. Thus, this silymarin-loaded solid dispersion would be useful for the enhancement of oral bioavailability and hepatoprotective activity of poorly water-soluble silymarin.     

Mechanochemical preparation of triptolide-loaded self-micelle solid dispersion with enhanced oral bioavailability and improved anti-tumor activity

Triptolide (TP), a compound isolated from a Chinese medicinal herb, possesses potent anti-tumor, immunosuppressive, and anti-inflammatory properties, but was clinically limited due to its poor solubility, bioavailability, and toxicity. Considering the environment-friendly, low-cost mechanochemical techniques and potential dissolution enhancement ability of Na₂GA, an amorphous solid dispersion (Na₂GA&TP-BM) consisting of TP and Na₂GA were well-prepared to address these issues. The performance of Na₂GA&TP-BM was improved through ball milling, such as from crystalline state to an amorphous solid dispersion, suitable nano micelle size and surface potential, and increased solubility. This change had a significant improvement of pharmacokinetic behavior in mice and could be able to extend the blood circulation time of the antitumor drug. Moreover, in vitro and in vivo anti-tumor study showed that Na₂GA&TP-BM displayed more potent cytotoxicity to tumor cells. The work illustrated an environment-friendly and safe preparation of the TP formulation, which was promising to enhance the oral bioavailability and antitumor ability of TP, might be considered for efficient anticancer therapy.     

阿苯达唑-盐酸盐的制备、表征及口服生物利用度的评价

目的 制备阿苯达唑（ABZ）-盐酸（HCl）盐（ABZ-HCl）,并对盐的固态性质、体外溶出行为、稳定性和生物利用度进行评价。方法 溶剂蒸发法制备结晶的ABZ-HCl,使用核磁共振氢谱（¹H-NMR）对制备的ABZ-HCl进行验证,通过粉末X射线衍射（PXRD）、动态水吸附（DVS）、热重分析（TGA）和差示扫描量热法（DSC）进行固态性质的表征;对药物盐进行表观溶解度和固有溶出速率（IDR）的测定以观察其在不同pH条件下溶解度和溶出速率;进行了ABZ-HCl在强光照射（4 500±500 lx）、高湿（92.5%±5% RH）和高温条件（50±2）℃,以及加速试验条件（40℃、75%±5% RH）的稳定性研究;评价ABZ、ABZ-HCl （25 mg·kg^-1）在大鼠体内的药动学行为差异。结果 通过¹H-NMR证实了ABZ-HCl的形成;ABZ和ABZ-HCl的PXRD图谱出现显著差异;DVS实验结果表明,ABZ原药的吸水性差,在90%相对湿度（RH）时吸水量仅为3.86%,且吸附与解吸附曲线基本重合,而ABZ-HCl在开始的0~20% RH范围内迅速吸收水分,随后质量缓慢增加,在RH达到90%时吸水量为37.65%,在解吸过程中,ABZ-HCl的吸附曲线和解吸曲线不一致,存在滞后现象;TGA和DSC实验结果表明,2种物质均无吸附水,ABZ-HCl较ABZ熔点降低;体外溶出实验结果显示ABZ-HCl的表观溶解度和IDR分别为ABZ的11.8、10.3倍;ABZ-HCl表现出良好的物理稳定性。体内药动学结果显示,与ig ABZ原料相比,ABZ-HCl的AUC_{0~24 h}和C_max均显著提高,分别提高了8.8和6.9倍。结论 所制备的ABZ-HCl可改善ABZ的溶解性能和口服生物利用度,且具有良好的物理稳定性。     

固体分散技术的研究进展

本文通过对近些年有关固体分散技术相关文献的查阅,重点介绍了固体分散体(SD)的载体材料、各种新型制备方法及其优缺点与稳定性三大方面内容;针对SD稳定性从载体与药物及其相关因素、其他外在条件两个方面提出了有效防止SD老化的方法;并对SD未来的研究方向给出了实际性建议与展望,为其广泛商业化生产提供了有力参考依据。固体分散技术在提高难溶性药物溶出度的同时也提高了其生物利用度,在实际生产中还可以根据需要制成各种缓控释制剂及所需的各种剂型,深入研究SD稳定性机制将有利于其进一步发展。     

Enhanced dissolution and oral bioavailability of valsartan solid dispersions prepared by a freeze-drying technique using hydrophilic polymers

This study aimed to improve the dissolution rate and oral bioavailability of valsartan (VAL), a poorly soluble drug using solid dispersions (SDs). The SDs were prepared by a freeze-drying technique with polyethylene glycol 6000 (PEG6000) and hydroxypropylmethylcellulose (HPMC 100KV) as hydrophilic polymers, sodium hydroxide (NaOH) as an alkalizer, and poloxamer 188 as a surfactant without using any organic solvents. In vitro dissolution rate and physicochemical properties of the SDs were characterized using the USP paddle method, differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and Fourier transform-infrared (FT-IR) spectroscopy, respectively. In addition, the oral bioavailability of SDs in rats was evaluated by using VAL (pure drug) as a reference. The dissolution rates of the SDs were significantly improved at pH 1.2 and pH 6.8 compared to those of the pure drug. The results from DSC, XRD showed that VAL was molecularly dispersed in the SDs as an amorphous form. The FT-IR results suggested that intermolecular hydrogen bonding had formed between VAL and its carriers. The SDs exhibited significantly higher values of AUC_0–24?h and C_max in comparison with the pure drug. In conclusion, hydrophilic polymer-based SDs prepared by a freeze-drying technique can be a promising method to enhance dissolution rate and oral bioavailability of VAL.     

Development and characterization of an atorvastatin solid dispersion formulation using skimmed milk for improved oral bioavailability

Atorvastatin has low aqueous solubility resulting in low oral bioavailability (12%) and thus presents a challenge in formulating a suitable dosage form. To improve the aqueous solubility, a solid dispersion formulation of atorvastatin was prepared by lyophilization utilising skimmed milk as a carrier. Six different formulations were prepared with varying ratios of drug and carrier and the corresponding physical mixtures were also prepared. The formation of a solid dispersion formulation was confirmed by differential scanning calorimetry and X-ray diffraction studies. The optimum drug-to-carrier ratio of 1:9 enhanced solubility nearly 33-fold as compared to pure drug. In vitro drug release studies exhibited a cumulative release of 83.69% as compared to 22.7% for the pure drug. Additionally, scanning electron microscopy studies suggested the conversion of crystalline atorvastatin to an amorphous form. In a Triton-induced hyperlipidemia model, a 3-fold increase in the lipid lowering potential was obtained with the reformulated drug as compared to pure drug. These results suggest that solid dispersion of atorvastatin using skimmed milk as carrier is a promising approach for oral delivery of atorvastatin.     

Evaluation of the bioavailability of hydrocortisone when prepared as solid dispersion

This study was conducted to formulate, characterize, and investigate the bioavailability of hydrocortisone (HCT) when prepared as solid dispersions. HCT was mixed in an organic solvent with polyethylene glycol 4000 (PEG 4000) and Kolliphor® P 407. Spray drying technique was employed to form a solid dispersion formulation at a specific ratio. Physical and chemical characterization of the formed particles were achieved using differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffractometry. Furthermore, comparative in vitro and in vivo studies were conducted between the formulated particles against neat HCT. The formulated solid dispersion showed elongated particles with leaf-like structure. Formation of new chemical bonds in the formed particle was suggested due to the change in the vibrational wave numbers and the significant improvement in the bioavailability of the dispersed particles proved the importance of this technique.     

Improving the solubility and bioavailability of dihydroartemisinin by solid dispersions and inclusion complexes

Dihydroartemisinin (DHA) is a poorly water-soluble drug that displays low bioavailability after oral administration. Attempts have been made to improve the solubility of DHA. Yet, no information is available concerning improved bioavailability. This study aimed to improve the water solubility of DHA by two systems: solid dispersions with polyvinylpyrrolidone (PVPK30, PVPK25, PVPK15) and inclusion complexes with hydroxypropyl-β-cyclodextrin (HPβCD), as well as improving the bioavailability of both systems. The phase transition of DHA with hydrophilic polymers was evaluated by X-ray diffraction (XRD) and differential scanning calorimetery (DSC). DHA became amorphous in DHA-HPβCD complexes and showed more amorphous behavior in XRD analyses with rise in molecular weight of PVP. Melting onset temperature of DHA decreased, while DSC thermograms revealed the peak area and enhanced enthalpy change (DH) in solid dispersions as well as inclusion complexes. DHA solubility was enhanced 84-fold in DHA-HPβCD complexes and 50-times in DHA-PVPK30. The improved solubility using the four polymers was in the following order: HPβCD > PVPK30 > PVPK25 > PVPK15. Values of area under curve (AUC) and half life (t_1/2) of DHA-PVPK30 were highest followed by DHA-HPβCD, DHA-PVPK15 and DHA-PVPK25. V_d/f of DHA-PVPK30 was 7-fold. DHA-HPβCD, DHA-PVPK15 and DHA-PVPK25 showed significantly different pharmacokinetic parameters compared with DHA solutions. The 95% confidence interval was meaningful in AUC and t_1/2. Pharmacokinetic parameters revealed that all four-test preparations were significantly more bioavailable than DHA alone.     

Improvement of dissolution rate of tacrolimus by solid dispersion technique

Tacrolimus has a poor solubility in water ranging from 4 to 12 μg mL^?1. The mean bioavailability is ~21 %.The present study was carried out with a view to enhance the dissolution rate of poorly water-soluble drug tacrolimus using Gelucire 44/14^® and Gelucire 50/13^® as carriers and lactose monohydrate as an adsorbent. A combination of melt and adsorption techniques was employed for the preparation of solid dispersions (SD) to make final product easy for handling. Phase solubility study was conducted to evaluate the effect of carriers on aqueous solubility of tacrolimus. In order to elucidate the mechanism of dissolution enhancement, solid state characteristics were investigated using Fourier transform infrared spectroscopy, differential scanning calorimetry and powder X-ray diffraction. Mathematical modeling of in vitro dissolution data indicated the best fitting with Korsemeyer–Peppas model and the drug release kinetics primarily as Fickian/anomalous diffusion. All prepared solid dispersions showed dissolution improvement compared to pure drug, with Gelucire 50/13^® as the superior carrier over Gelucire 44/14^®. Almost similar dissolution profile was obtained as a function of storage time; this can be explained by no change in XRD and DSC pattern after 45 days storage period.     

尼莫地平干乳的家兔口服生物利用度研究

目的以尼莫地平为模型药物,对其干乳、脂肪乳、片剂3种制剂的生物利用度进行比较研究。方法新西兰大白兔单次口饲尼莫地平制剂,用HPLC法测定血浆中尼莫地平的浓度,根据血药浓度计算生物利用度。结果兔口饲尼莫地平后,干乳和脂肪乳的生物利用度均大于片剂,差异具有统计学意义;干乳和脂肪乳的生物利用度比较,差异无统计学意义。与片剂相比尼莫地平干乳和脂肪乳均具有一定的缓释作用。结论干乳和脂肪乳能较大地提高尼莫地平兔口服生物利用度,且具有缓释作用。     

固体分散体在提高难溶性药物口服生物利用度中的应用

固体分散体在提高难溶性药物溶出度和口服生物利用度中的应用引起了药学工作者的关注,本文综述了固体分散体常用载体、常用的溶剂、提高难溶性药物溶出速率的机制和制备方法以及其他替代的方法,以期将难溶性药物制备为固体分散体提供参考。     

Preparation of curcumin self-micelle solid dispersion with enhanced bioavailability and cytotoxic activity by mechanochemistry

An amorphous solid dispersion (SD) of curcumin (Cur) with disodium glycyrrhizin (Na₂GA) was prepared by mechanical ball milling. Curcumin loaded micelles were self-formed by Na₂GA when SD dissolved in water. The physical properties of Cur SD in solid state were characterized by differential scanning calorimetry, X-ray diffraction studies, and scanning electron microscope. The characteristics of the sample solutions were analyzed by reverse phase HPLC, UV–visible spectroscopy, ¹H NMR spectroscopy, gel permeation LC, and transmission electron microscopy. In vitro cytotoxic tests demonstrated that Cur SD induced higher cytotoxicity against glioblastoma U-87?MG cells than free Cur. Besides, an improvement of membrane permeability of Cur SD was confirmed by parallel artificial membrane permeability assay. Further pharmacokinetic study of this SD formulation in rat showed a significant ～19-fold increase of bioavailability as comparing to free Cur. Thus, Cur SD provide a more potent and efficacious formulation for Cur oral delivery.