Mechanism of increased dissolution of diazepam and temazepam from polyethylene glycol 6000 solid dispersions

Solid dispersion literature, describing the mechanism of dissolution of drug-polyethylene glycol dispersions, still shows some gaps; (A). only few studies include experiments evaluating solid solution formation and the particle size of the drug in the dispersion particles, two factors that can have a profound effect on the dissolution. (B). Solid dispersion preparation involves a recrystallisation process (which is known to be highly sensitive to the recrystallisation conditions) of polyethylene glycol and possibly also of the drug. Therefore, it is of extreme importance that all experiments are performed on dispersion aliquots, which can be believed to be physico-chemical identical. This is not always the case. (C). Polyethylene glycol 6000 (PEG6000) crystallises forming lamellae with chains either fully extended or folded once or twice depending on the crystallisation conditions. Recently, a high resolution differential scanning calorimetry (DSC)-method, capable of evaluating qualitatively and quantitatively the polymorphic behaviour of PEG6000, has been reported. Unraveling the relationship between the polymorphic behavior of PEG6000 in a solid dispersion and the dissolution characteristics of that dispersion, is a real gain to our knowledge of solid dispersions, since this has never been thoroughly investigated. The aim of the present study was to fill up the three above mentioned gaps in solid dispersion literature. Therefore, physical mixtures and solid dispersions were prepared and in order to unravel the relationship between their physico-chemical properties and dissolution characteristics, pure drugs (diazepam, temazepam), polymer (PEG6000), solid dispersions and physical mixtures were characterised by DSC, X-ray powder diffraction (Guinier and Bragg-Brentano method), FT-IR spectroscopy, dissolution and solubility experiments and the particle size of the drug in the dispersion particles was estimated using a newly developed method. Addition of PEG6000 improves the dissolution rate of both drugs. Mechanisms involved are solubilisation and improved wetting of the drug in the polyethylene glycol rich micro-environment formed at the surface of drug crystals after dissolution of the polymer. Formulation of solid dispersions did not further improve the dissolution rate compared with physical mixtures. X-ray spectra show that both drugs are in a highly crystalline state in the solid dispersions, while no significant changes in the lattice spacings of PEG6000 indicate the absence of solid solution formation. IR spectra show the absence of a hydrogen bonding interaction between the benzodiazepines and PEG6000. Furthermore, it was concluded that the reduction of the mean drug particle size by preparing solid dispersions with PEG6000 is limited and that the influence of the polymorphic behavior of PEG6000 (as observed by DSC) on the dissolution was negligible.     

Improvement of the dissolution kinetics of SR 33557 by means of solid dispersions containing PEG 6000

Solid dispersions of SR 33557 in preparations containing from 30 to 80% w/w polyethylene glycol 6000 (PEG 6000) were prepared by the fusion method. The solubility of the drug substance either alone or in solid dispersions was determined in pH 1.2 and 4.5 media (extraction fluid NFXII, without enzyme). A large increase in the solubility was noted from the 80% w/w PEG preparation. A wettability study performed by measuring the contact angle on tablets of either drug substance or PEG 6000, or solid dispersions, revealed a minimal contact angle for the 80% w/w PEG 6000 solid dispersion (eutectic composition of SR 33557/PEG 6000 phase diagram). Dissolution kinetic analysis performed at pH 1.2 on all solid dispersions, on the physical mixtures containing 70 and 80% w/w PEG 6000, and on SR 33557 alone, showed a maximum release rate (100%) for the solid dispersions containing 70 and 80% w/w PEG 6000. The dissolution rate of the physical mixtures was faster than that of the drug substance alone but remained, however, lower than that of the solid dispersions, at the same composition. It was also observed that the dissolution rate, at pH 1.2 and 4.5, of the 70% w/w PEG 6000 solid dispersion was practically pH independent, which was not the case for the drug substance alone. The latter solid dispersion showed a slowing down of the dissolution kinetics after 3 months storage at 50°C whereas no change in the dissolution rate was observed following storage for 12 months at 25°C.     

Flow-injection fluorimetric determination of 1,4-benzodiazepines in pharmaceutical formulations after acid hydrolysis

A simple, rapid and fully automated flow injection method with fluorimetric detection after hydrolysis with H2SO4 in ethanolic or methanolic medium at room temperature has been developed for the determination of 1,4-benzodiazepines (oxazepam, diazepam and nitrazepam) in pharmaceutical formulations. The calibration curves are linear in the ranges (mg ml(-1)) of oxazepam (0.025-0.150), diazepam (0.010-0.125) and nitrazepam (0.010-0.150), with detection limits of 0.01, 0.005 and 0.005 mg ml(-1), respectively, and RSD (1% (n = 10). The measurement throughput is 60 h(-1) using a 200-microl sample volume obtained by the direct dissolution of formulations in alcohol.     

Toxicological and pharmacological investigations of pinazepam (7-chloro-1-propargyl-5-phenyl-3H-1,4-benzodiazepin-2-one): a new psychotherapeutic agent.

The pharmacological and toxicological properties of 7-chloro-1-propargyl-5-phenyl-3H-1,4-benzodiazepin-2-one (pinazepam) were investigated and compared with those of diazepam. In mouse and rat acute toxicity, in rat motor coordination and in rat metrazol convulsion tests pinazepam was compared with oxazepam too. Pinazepam, which is characterized by the presence of a propargylic side chain, showed a lower toxicity, hypnotic activity and muscular-relaxant activity than diazepam. Pinazepam and diazepam showed, however, similar activity in reducing aggressive behaviour in mice, stimulating the exploratory behaviour in rats and in potentiating hexobarbital narcosis. No clear-cut differences were observed in the anticonvulsant properties of the two drugs when tested against metrazol, strychnine and electroshock induced seizures. Pinazepam differs from diazepam for its longer duration of action. The main metabolic product found in the urine of rats and dogs treated with pinazepam was oxazepam.     

水飞蓟素-聚乙二醇6000固体分散体系的制备及其特征考察

目的制备水飞蓟素固体分散体，加快药物的溶出，并进行特征考察。方法以聚乙二醇6000(PEG6000)为材料，采用熔融法将难溶性药物水飞蓟素制成固体分散体，通过体外释药试验考察固体分散技术对水飞蓟素的增溶作用，并以X-射线粉末衍射、傅立叶变换红外光谱(FT-IR)考察水飞蓟素固体分散体的特性。结果与原药比较，固体分散体中药物的释放速率明显增大，PEG6000固体分散体系能显著加快水飞蓟素的溶出。X-射线粉末衍射分析表明，PEG6000及药物在固体分散体中的晶格点阵面间距离、衍射峰位移及其相对强度等均发生了规律性变化，FT-IR分析表明PEG6000与药物间无相互作用。结论PEG6000固体分散体系的对难溶性药物溶出和扩散的加快，与载体材料和药物的晶格参数的改变密切相关。     

尼群地平固体分散体的研制

为了提高难溶性药物尼群地平的溶出度,制备了其固体分散体,考察其体外溶出度并与原料药作对照,筛选出较佳的处方。     

Physicochemical characterization of solid dispersions of the antiviral agent UC-781 with polyethylene glycol 6000 and Gelucire 44/14

The purpose of this study was to prepare and characterize solid dispersions of the antiviral thiocarboxanilide UC-781 with PEG 6000 and Gelucire 44/14 with the intention of improving its dissolution properties. The solid dispersions were prepared by the fusion method. Evaluation of the properties of the dispersions was performed using dissolution studies, differential scanning calorimetry, Fourier-transform infrared spectroscopy and X-ray powder diffraction. To investigate the possible formation of solid solutions of the drug in the carriers, the lattice spacings [d] of PEG 6000 and Gelucire 44/14 were determined in different concentrations of UC-781. The results obtained showed that the rate of dissolution of UC-781 was considerably improved when formulated in solid dispersions with PEG 6000 and Gelucire 44/14 as compared to pure UC-781. From the phase diagrams of PEG 6000 and Gelucire 44/14 it could be noted that up to approximately 25% w/w of the drug was dissolved in the liquid phase in the case of PEG 6000 and Gelucire 44/14. The data from the X-ray diffraction showed that the drug was still detectable in the solid state below a concentration of 5% w/w in the presence of PEG 6000 and Gelucire 44/14, while no significant changes in the lattice spacings of PEG 6000 or Gelucire 44/14 were observed. Therefore, the possibility of UC-781 to form solid solutions with the carriers under investigation was ruled out. The results from infrared spectroscopy together with those from X-ray diffraction and differential scanning calorimetry showed the absence of well-defined drug–polymer interactions.     

浙贝提取物固体分散体的制备及溶出特性研究

目的：制备浙贝提取物固体分散体,考察其中贝母素甲及贝母素乙的溶出效果,从而确定制备的最佳方法和最佳比例。方法：选择聚乙二醇6000（PEG6000）与聚乙烯吡咯烷酮（PVP K30）两种载体材料,分别采用熔融法和溶剂法制备浙贝提取物固体分散体;通过比较提取物、固体分散体的溶出性能,确定最佳工艺。结果：使用HPLC-ELSD法测定贝母素甲及贝母素乙的溶出量,结果准确、可靠、稳定。制备成固体分散体能显著提高贝母素甲及贝母素乙的体外溶出速度;PEG6000作为载体的浙贝提取物固体分散体溶出速度快于PVP K30为载体的浙贝提取物固体分散体。结论：以PEG6000为载体,采用熔融法制备的药物/载体比例为1∶6的固体分散体能显著提高浙贝提取物中贝母素甲及贝母素乙的溶出速率。     

Metabolic Rearrangements of 1,4-Benzodiazepine Derivatives

1. Formation of quinazolines from 1,4-benzodiazepines represents a minor metabolic pathway.

2. In incubations of rat liver microsomal preparations with oxazepam, lorazepam, medazepam, diazepam, and chlorazepate, the quinazolin-2-ones were formed in amounts of less than 1% of added substrate without phenobarbital pre-treatment and to a maximum of 2% with phenobarbital pre-treatment.

3. 3-Hydroxy-1,4-benzodiazepines, e.g., oxazepam and 3-hydroxydiazepam, are metabolic precursors in quinazolin-2-one formation, whereas 3-oxo derivatives were excluded as metabolic intermediates.

4. 3-Methyl analogues of diazepam also yielded quinazolinones by elimination of position 3 of the diazcpine ring and additionally gave the 2-acetylquinazo-line and the 2-ethan-α-ol-quinazoline as major metabolites presumably via the same intermediate.

5. The 3-carboxylate chlordiazepate (chlorazepate) was first metabolized to oxazepam and subsequently to the quinazolin-2-one.     

缬沙坦固体分散体的制备及体外溶出度研究

目的采用冷冻干燥法制备缬沙坦（Valsartan）速释固体分散体（SD）来提高其体外溶出度。方法分别以羟丙甲基纤维素（HPMC）、聚乙二醇6000（PEG6000）、聚乙烯吡咯烷酮k30（PVPk30）为载体,十二烷基硫酸钠（SDS）为表面活性剂来制备不同比例的缬沙坦固体分散体,通过测定体外溶出度,来选择最优辅料及比例,结果当以PEG6000载体,SDS为表面活性剂时,且药物：PEG6000：SDS=1：5：1％时药物呈现了很好的水溶性。结论在5min时即可溶出90％以上,很大程度上提高了缬沙坦的体外溶出度。     

Synthesis and pharmacological activity and some derivatives of 1-phenyl-1,2,3,4-tetrahydro-5H-1,4-benzodiazepin-5-one.

4-N-Alkylamino derivatives and corresponding ammonium quaternary salts of tetrahydro-1,4-benzodiazepin-5-one were synthesized and evaluated for psychotropic activity in mice by ip via. This study was also extended to some nitro and amino derivatives of tetrahydro-1,4-benzodiazepin-5-one. Compounds were devoid of tranquilizing activity and in comparison with two classical benzodiazepines, chlordiazepoxide and diazepam, they showed high toxicity and little or no effect on motor coordination, motor activity, and maximal electroshock. On some "in vitro" tests the compounds exhibited pharmacological properties when they were used at high concentrations.     

Physical Stability of Solid Dispersions Containing Triamterene or Temazepam in Polyethylene Glycols

The effect of storage on the physical stability of solid dispersions of triamterene or temazepam in polyethylene glycols was studied using differential scanning calorimetry (DSC), particle-size analysis and dissolution methods. The enthalpies of fusion of the carriers, without included drug and previously fused and crystallized, increased on storage. Analysis of similarly treated solid dispersions, containing either 10% temazepam or 10% triamterene, showed that each drug influenced the morphology of the polyethylene glycol (PEG). The enthalpies and melting points of the solidus components of the dispersions' carriers were initially reduced after preparation, but on storage these increased. The particle sizes of the drugs dispersed in the PEGs increased on storage. The changes in dissolution after storage of triamterene or temazepam dispersions were smaller for dispersions in PEG 1500 than for dispersions in PEGs of higher molecular weight (PEG 2000, PEG 4000 or PEG 6000) in which the reduction in dissolution was particularly marked during the first month of storage. The rank order of changes in dissolution were PEG 1500 ? PEG 2000 < PEG 4000 ～ PEG 6000.     

布格呋喃固体分散体的体外研究

布格呋喃(buagafuran,AF-5)是以( )香芹酮为起始原料通过立体选择性合成的沉香呋喃类化合物[1].它具有显著的抗焦虑作用,毒副作用低,市场前景广阔.布格呋喃为油状液体,脂溶性强,不溶于水.用植物油稀释进行小鼠灌胃,抗焦虑活性与空白组比较无统计学意义,不能较好地发挥药效.室温放置易发生降解,化学稳定性差.这些缺     

布渣叶总黄酮固体分散体的制备及体外溶出度测定

目的:采用固体分散体技术考察不同载体材料对布渣叶总黄酮提取物溶出度的影响.方法:选择不同种类的聚乙二醇、泊洛沙姆、聚乙烯吡咯烷酮为载体材料,与布渣叶总黄酮提取物按质量比1:4混合均匀,分别用熔融法和溶剂法制备固体分散体,以固体分散体中总黄酮、牡荆苷、异牡荆苷、水仙苷的90 min累积溶出度作为评价指标,比较不同载体制备的固体分散体的释药速率,并采用X射线衍射和红外光谱分析对其物相特征进行研究.结果:与布渣叶总黄酮提取物和物理混合物相比,以PEG和泊洛沙姆所制备的布渣叶提取物固体分散体中总黄酮、牡荆苷、异牡荆苷和水仙苷的体外溶出度与溶出速率均明显增加.其中以泊洛沙姆407为载体材料所制备的固体分散体中总黄酮体外溶出度最佳,90 min累积溶出度达到84%;以PEG 6000为载体材料所制备的固体分散体中牡荆苷、异牡荆苷、水仙苷体外溶出度最佳,90 min累积溶出度均达96%以上.结论:采用固体分散体技术,选择PEG 6000或泊洛沙姆407为载体制备布渣叶总黄酮提取物固体分散体,对提取物中脂溶性成分的溶出有明显改善作用.     

Physicochemical characterization and dissolution of norfloxacin/cyclodextrin inclusion compounds and PEG solid dispersions

Increase in the poor water solubility and dissolution rate of norfloxacin was studied. Two systems were used: solid dispersion with PEG 6000 prepared using the fusion method and inclusion complexes with cyclodextrins (β-cyclodextrin and HP-β-cyclodextrin) obtained by freeze-drying. IR spectrophotometry, X-ray diffractometry, and differential scanning calorimetry showed differences between norfloxacin/cyclodextrin complexes and their corresponding physical mixtures, but not between norfloxacin/PEG 6000 solid dispersions and their corresponding physical mixtures. The solubility and dissolution rate of norfloxacin were significantly increased with PEG solid dispersions and cyclodextrin complexes as well as with norfloxacin-CD physical mixtures. However, enhancement was not statistically different either among various cyclodextrin complexes, or between solid dispersions and cyclodextrin complexes.     

Physical stability of solid dispersions of the antiviral agent UC-781 with PEG 6000, Gelucire 44/14 and PVP K30

This paper describes the physical stability of solid dispersions of UC-781 with PEG 6000, Gelucire 44/14 and PVP K30 prepared by the solvent and melting methods. The concentration of the drug in the solid dispersions ranged from 5 to 80% w/w. The solid dispersions were stored at 4-8 and 25 degrees C (25% RH), then their physicochemical properties were analysed by differential scanning calorimetry (DSC), X-ray powder diffraction and dissolution studies as a function of storage time. The DSC curves of solid dispersions of UC-781 with PVP K30 did not show any melting peaks corresponding to UC-781 after storage, indicating no recrystallization of the drug. The DSC data obtained from PEG 6000 and Gelucire 44/14 showed some variations in melting peak temperatures and enthalpy of fusion of the carriers. It was shown that the enthalpy of fusion of PEG 6000 in the dispersions increased after storage; it was more pronounced for samples stored at 25 degrees C compared to those at 4-8 degrees C indicating the reorganization of the crystalline domains of the polymer. Similarly, the enthalpy of fusion of Gelucire 44/14 in the solid dispersions increased as a function of time. Dissolution of UC-781 from all solid dispersions decreased as a function of storage time. While these observations concurred with the DSC data for all solid dispersions, they were not reflected by X-ray powder diffraction data. It was concluded that it is the change of the physical state of the carriers and not that of the drug, which is responsible for the decreased dissolution properties of the solid dispersions investigated.     

In vitro and in vivo evaluation of carbamazepine-PEG 6000 solid dispersions

The present work extended previous physico-chemical investigations on the effects of solid dispersion on the solubility, the dissolution rate and the pharmacokinetic profile of carbamazepine. Solubility studies showed a linear increase in carbamazepine solubility with the increase of PEG 6000 concentration. There is no marked difference between physical mixtures and solid dispersions for the enhancement of carbamazepine solubility by PEG 6000. Less than 60% of pure carbamazepine was dissolved in 90 min. Physical mixtures (carbamazepine phase III) and solid dispersions (carbamazepine phase II) dissolution rates were higher in comparison of the parent drug. The dissolution of carbamazepine phase III was more pronounced than that evoked by the phase II. The dissolution profiles indicated that the percentage of the drug dissolved was dependent on the proportion of PEG 6000. In solid dispersions there was a remarkable enhancement in the dissolution rates of the drug in the vicinity of the eutectic composition as compared with those of corresponding physical mixtures. Hence, the optimum value for the solid dispersion was 80.5+/-1.7% of carbamazepine having dissolved within the first 10 min compared to 40+/-1% for the corresponding physical mixtures of the same composition. Statistical analysis of pharmacokinetic parameters confirmed that the carbamazepine:PEG 6000 binary systems displayed higher bioavailability of the drug than the pure carbamazepine. The area under the curve (AUC) values highlighted the evidence that only slight differences in the bioavailability of the drug occur between physical mixtures and solid dispersions prepared at the 80:20 and 50:50 drug:carrier compositions. However, the mean normalized plasma concentrations showed that standard error deviations are rather wide intervals for pure drug and physical mixtures in comparison to solid dispersions. One additional interesting point to consider is the disappearance of the multiple peaks on the individual kinetic curves of the 50:50 solid dispersion composition. Furthermore, our investigations have highlighted the interest of solid dispersions prepared at -eutectic composition as our preliminary data show that the plasma concentration (C(5h)) of the drug for the 15:85 dispersed sample containing 150 mg of carbamazepine is not significantly different from that obtained for the 50:50 dispersed sample containing 300 mg of the drug.     

硝苯地平固体分散体制备工艺的研究

目的利用固体分散技术将硝苯地平制成固体分散体,提高其体外溶出速率。方法分别以聚乙二醇6000(PEG6000)、聚乙二醇4000(PEG4000)、聚乙烯吡咯烷酮K30(PVPK30)、泊洛沙姆188(Pluronic F68)等为载体,用熔融法、溶剂法、溶剂-熔融法和喷雾干燥法制备硝苯地平固体分散体。采用差热分析法(DTA)分析药物在固体分散体中的存在状态,并进行体外溶出度试验。结果各种固体分散体均能加快药物的溶出速率,并且随着载体在固体分散体中的比例增大,溶出速率增大。DTA分析显示硝苯地平在PVPK30的固体分散体中以微细结晶存在。结论将硝苯地平制成固体分散体能显著提高硝苯地平的体外溶出速率。     

The properties of solid dispersions of indomethacin or phenylbutazone in polyethylene glycol

The effects of molecular weight of polyethylene glyeols (PEGs) on the dissolution rates and crystallinity of its solid dispersions with indoniethacin and phenylbutazone have been examined. The dissolution rates of both solid-dispersed drugs decreased as the molecular weight of PEG increased. The indoniethacin dissolution profiles were essentially linear using constant surface area disc methodology and a limiting dissolution rate of about 10.6 mg · min⁻¹ was observed. The phenylbutazone dissolution profiles were. however, generally linear-curvic usually giving lower release rates than the comparative indomethacin weight fractions. A limiting dissolution rate for the linear portions of the profiles was about 1.8 mg · min⁻¹. Infra-red spectra indicated that the differences between the two drugs could partly be explained on the basis of PEG crystallinity. Generally bands in the ranges 1100–1130 and 1200–1400 cm⁻¹ were poorly differentiated in indomethacin dispersions (PEG 1500, PEG 4000 and PEG 6000) but were better differentiated in phenylbutazone dispersions (PEG 4000, PEG 6000 and PEG 20,000). A greater proportion of amorphousness within the PEG moiety was predicted in indomethacin dispersions by the appearance of a new weak band at 1326 cm⁻¹ and by a decrease in intensity of the band at 845 cm⁻¹ at the expense of the peak at 960 cm⁻¹. The evidence was supported by differential scanning calorimetry. The heats of fusion were 44.7, 46.4, 47.2 and 39.5 cal · g⁻¹ for PEG 1500, PEG 4000, PEG 6000 and PEG 20.000 respectively. Heats of fusion for indomethacin dispersions (2, 5 and 10% drug) were generally lower than for the corresponding values for phenylbutazone dispersions-with the exception of PEG 20,000 dispersions. For example, values were obtained of 30.6 and 37.9 cal · g⁻¹ for PEG 1500 dispersions containing 10% indomethacin and phenylbutazone, respectively.     

固体分散体提高银杏叶片溶出度的研究

目的:通过制备固体分散体提高银杏叶片中银杏叶提取物(EGb)的溶出度.方法:采用溶剂熔融法、喷雾干燥法制备聚乙二醇6000(PEG 6000)和聚乙烯吡咯烷酮K17(PVPK17)2种载体材料、不同比例的固体分散体,并比较固体分散体、物理混合物和EGb、市售普通片的溶出特性.对EGb-PEG 6000固体分散体进行差示热扫描(DSC)分析.结果:溶剂熔融法和喷雾干燥法可制备不同比例的PEG 6000,PVPK17的EGb固体分散体,EGb-PEG 6000(1:2)固体分散体片溶出度增加明显,且增溶效果优干EGb-PVPK17固体分散体.结论:EGb-PEG 6000(1:2)固体分散体能有效提高银杏叶片的溶出度.