Dissolution characteristics of cylindrical particles and tablets

In this paper, dissolution characteristics of primary-particles and compressed tablets were investigated by experiments using a mathematical model. For the primary-particle, it was found that the dissolution rate increased with a decrease in the particle size. Assuming that primary-particles of size distribution were of cylindrical shape and that the dissolution occurs from the total external surface, an extended Nernst–Noyes–Whitney equation fitted to the experimental data well. As the influences of particle size and shape on thickness of a diffusion-boundary film were found to be quite low, the dissolution rate was considered to be affected by the specific surface area dominantly. Furthermore, the same model was applied to a compressed tablet and fitted to the data well. Though the rate constant obtained were not affected by the properties of primary-particles forming the tablet, it was found to increase with the apparent voidage which occupies the inter-particle volume of tablet diluent among less soluble particles. Consequently, an increase in the apparent voidage is presumed to accelerate penetration of water into the internal voids of the tablet. Thus, the dissolution going, the effective surface area inside the tablet is considered to be extended.     

Determination of deferasirox particle size distribution via laser diffraction and its application in establishing a correlation between particle size and drug dissolution in vitro

Deferasirox is the first-line drug for iron overload due to thalassemia in adults and pediatric patients. It is classified as a type II compound in the Biopharmaceutics Classification System, and thus the particle size of its active pharmaceutical ingredient (API) should be strictly controlled during the manufacturing process. In the present study, laser diffraction was adopted to measure the particle size distribution of deferasirox API. We also developed and validated an accurate and convenient method by investigating important optical parameters and sample dispersing conditions. The relative standard deviation values, namely, d (0.1), d (0.5), d (0.9), and d (4,3), measured via methodology validation and actual sample measurement were < 3%. The dissolution curves of several batches of dispersible tablets prepared using deferasirox with different particle sizes were compared in the four dissolved media to investigate the influence of particle size on drug dissolution in vitro. Results indicated that the particle size distribution of deferasirox API significantly affected the release of its dispersible tablet.     

Comparison of two dissolution apparatuses with correlation of in vitro-in vivo data for prednisone and prednisolone tablets

Dissolution profiles in 0.1N hydrochloric acid using both the paddle stirrer apparatus and the spin filter apparatus were obtained for prednisone tablets made by seven different manufacturers and prednisolone tablets made by eight different manufacturers. Dissolution parameters were correlated with results obtained in three human bioavailability trials which were previously reported. Also, results obtained in one apparatus were correlated with those obtained in the other apparatus. Such correlations may be useful in the setting of in vitro dissolution rate specifications for commerical prednisone and prednisolone tablets.     

The influence of the particle size of hydroxypropylmethylcellulose K15M on its hydration and performance in matrix tablets

The dissolution rate of propranolol hydrochloride from matrices containing different sized fractions of hydroxypropylmethylcellulose K15M has been examined. Generally, the release rate decreased as the particle size of hydroxypropylmethylcellulose was reduced from > 355 μM to 150–210 μM. Further reduction in size caused no further decrease in dissolution rate. Burst release of propranolol occurred at the extremes of large particle size and low matrix contents of hydroxypropylmethylcellulose K15M. Measurements of surface area by nitrogen adsorption indicated that all the sieve fractions of hydroxypropylmethylcellulose were poorly porous. Water uptake studies, measured by differential scanning calorimetry, suggested that initially the larger sized fraction of hydroxypropylmethylcellulose imbibed water faster than the smaller sized fraction.     

激光粒度仪测定单硝酸异山梨酯缓释片中间产品粒度的方法学研究

目的 建立测定单硝酸异山梨酯缓释片中间产品粒度分布的方法。方法 采用Malvern Mastersizer 3000型激光粒度分析仪,Aero S型干法进样器。激光散射法干法检测参数为：样品折射率1.52、漏斗池高度1.0 mm、遮光度范围0.8%～3.0%、分散气体压力2.0 bar、进样速度50%、样品测量时间25 s。结果 同一批供试品,平行测定6次,不同操作人员在不同时间、使用相同仪器和相同方法,测得粒度分布结果的RSD值小于1.0%;三个批次供试品,相同操作人员使用相同仪器和相同方法测得批次间粒度分布结果的RSD值小于2.0%。结论 该方法重现性好、准确度高,操作简便,可用于单硝酸异山梨酯缓释片中间产品粒度分析。     

A new approach in the prediction of the dissolution behavior of suspended particles by means of their particle size distribution

Though various attempts have been made in literature to model the particle size distribution of an active pharmaceutical ingredient (API) in function of the required release profile of the pharmaceutical product, so far one has not succeeded to develop a universal approach in the correlation of particle size distribution and in vitro dissolution data. In this publication, a new approach is presented on the use of particle size distribution data in the prediction of the in vitro dissolution profile of a suspension formulation. For this purpose, various theoretical experiments were done simply on paper and based on the Noyes–Whitney [A.A. Noyes, W.R. Whitney, J. Am. Chem. Soc. 19 (1897) 930–934] equation, the normalized dissolution profiles of various imaginary size distributions were calculated. For each size distribution, its weighted mean diameters were then calculated. Based on these theoretical data, a model could be developed which scientifically explains the dissolution profile of a suspension in function of its volume-weighted mean particle size (D[4, 3]). The applicability of this correlation model could experimentally be confirmed by evaluation of laser diffraction and in vitro dissolution data as they were obtained for different batches of a suspension formulation. This new approach in the correlation between particle size and dissolution may be an important analytical tool in the engineering of the particle size distribution of drug substance, and more precisely monitoring the D[4, 3] volume-weighted mean diameter may allow one to model the dissolution profile of a suspension formulation and thereby its in vivo release profile.     

Dissolution and assaying of multicomponent tablets by chemometric methods using computer-aided spectrophotometer

Dissolution of three component tablets containing paracetamol (APAP), propyphenazone (PP), and caffeine (CAF) was carried out by USP paddle method. Three chemometric methods; inverse least square (ILS), principal component regression (PCR) and partial least squares (PLS) were applied to simultaneous assay of APAP, PP and CAF in tablets. The PCR, PLS and ILS methods were applied to simultaneous dissolution APAP, PP and CAF in tablets using a double beam UV-Vis spectrophotometer without any chemical separation and any graphical treatment of the overlapping spectra of three drugs. Twenty two mixture solutions in different concentrations were prepared in simulated gastric juice (SGJ, USP) for the chemometric calibrations as training set. The absorbance data matrix was obtained by measuring the absorbance at 14 wavelength points (from 222.5 to 292.5 nm) with the intervals of 5 nm (Deltalambda=5 nm) in the spectral region between 200 and 310 nm. Training set and absorbance data were used for the calibrations of chemometric methods. The developed calibrations were tested for the previously prepared solutions of mixture of three drugs for the validation of the assay method. The chemometric calculations were performed by using the 'MAPLE VRSQUO; software. The results of three chemometric methods were statistically compared with each other. These chemometric calibrations were successfully applied to the content uniformity and dissolution of the multicomponent tablets without any separation procedure. The synthetic mixtures of three drugs were used for the validity of the calibrations. Means recoveries (percent) and relative standard deviation of PLS, PCR and ILS methods were found to be 100.1+/-0.6, 101.4+/-1.6 and 100.1+/-0.6 for APAP; 100.9+/-3.2, 102.0+/-3.3 and 100.9+/-3.2 for PP; 99.9+/-3.5, 101.6+/-3.3 and 99.9+/-3.2 for CAF, respectively. Dissolution profiles of three component tablets were performed. More than 95% of drugs were dissolved within 15 min. All of the three-chemometric methods in this study can be satisfactorily used for the quantitative analysis and for dissolutions test of multicomponent dosage form.     

Relationship between dissolution and bioavailability for nimodipine colloidal dispersions: the critical size in improving bioavailability

To compare the dissolution and bioavailability for nimodipine microcrystals and nanocrystals, and to determine the critical size range in improving the oral absorption of nimodipine. Nimodipine microcrystals and nanocrystals were prepared using a microprecipitation method. The particle size was determined with a laser diffraction method. X-ray powder diffraction was applied to inspect the potential crystal form transition. The aqueous solubility was determined by shaking flasks, and the dissolution behavior was evaluated using the paddle method. The pharmacokinetics was performed in beagle dogs in a crossover experimental design. Three nimodipine colloidal dispersions (16296.7, 4060.0 and 833.3 nm) were prepared, respectively. Nimodipine had undergone crystal form transition during microprecipitation process, but experienced no conversion under the high-pressure homogenization. The colloidal dispersions did not show any difference in aqueous equilibrium solubility. Additionally, the three formulations also displayed similar dissolution curves in purified water and 0.05% SDS. The AUC for dispersions of 4060.0 and 833.3 nm sizes was 1.69 and 2.59-fold higher than that for 16296.7 nm system in dogs. To sum up, the critical particle size was found to be within the range of 833.3-4060.0 nm (average volume-weighted particle size) in improving the bioavailability of nimodipine, and dissolution performance was not an effective index in evaluating the bioavailability for nimodipine colloidal dispersions.     

地榆升白片与利血生治疗白细胞减少症的疗效比较

目的观察地榆升白片联合利血生片剂治疗白细胞减少症的临床效果。方法依就诊顺序将103例白细胞减少症患者分为3组:A组口服地榆升白片,B组口服利血生片,C组(地榆升白片+利血生片)联合用药,持续治疗2个疗程。结果 C组治疗显效率为43.6%(17/39),总有效率为87.2%(34/39),显著高于其他两组(P<0.05);出现部分反酸、轻度胃部不适病例,复发率为14.7%,显著低于其他两组(P<0.01)。结论地榆升白片联合利血生对治疗白细胞减少症有确切疗效,不良反应少,临床上可推广应用。     

布洛芬粉粒的溶出研究：粒径大小的影响及二种不同粒径粉粒混合后溶出过程的模拟

本文围绕粒径大小对布洛芬粉末溶出的影响进行了一系列实验研究。在非漏槽条件下比较了六种筛分粒径（＜65，65－74，74－91，91－125，125－150,和150－200μm）的溶出速率。粒径大于74μm的粉末溶出速度随粒径的减小而增加。另一方面，粒径小于74μm的粉末则呈不同的溶出曲线，起始较慢，这可能是由研磨后形成的颗粒静电引起。本文还进行了两种粉末按不同比例混合后的溶出实验，用每一组分的溶出数据模拟了二组分混合体系的溶出过程，几乎在全部溶出过程中模拟曲线都能很好地与测定值吻合，对二组分混合体系的溶出进行评估和模拟有可能用在多粒径粉末混合体系的溶出速度的评估及预测中。     

The effects of particle size,shape, density and flow characteristics on particle margination to vascular walls in cardiovascular diseases

Introduction: Vascular-targeted drug delivery is a promising approach for the treatment of atherosclerosis, due to the vast involvement of endothelium in the initiation and growth of plaque, a characteristic of atherosclerosis. One of the major challenges in carrier design for targeting cardiovascular diseases (CVD) is that carriers must be able to navigate the circulation system and efficiently marginate to the endothelium in order to interact with the target receptors.

Areas covered: This review draws on studies that have focused on the role of particle size, shape, and density (along with flow hemodynamics and hemorheology) on the localization of the particles to activated endothelial cell surfaces and vascular walls under different flow conditions, especially those relevant to atherosclerosis.

Expert opinion: Generally, the size, shape, and density of a particle affect its adhesion to vascular walls synergistically, and these three factors should be considered simultaneously when designing an optimal carrier for targeting CVD. Available preliminary data should encourage more studies to be conducted to investigate the use of nano-constructs, characterized by a sub-micrometer size, a non-spherical shape, and a high material density to maximize vascular wall margination and minimize capillary entrapment, as carriers for targeting CVD.     

Influence of particle size and preparation methods on the physical and chemical stability of amorphous simvastatin

This study investigated the factors influencing the stability of amorphous simvastatin. Quench-cooled amorphous simvastatin in two particle size ranges, 150-180 μm (QC-big) and ?10 μm (QC-small), and cryo-milled amorphous simvastatin (CM) were prepared, and their physical and chemical stability were investigated. Physical stability (crystallization) of amorphous simvastatin stored at two conditions was monitored by X-ray powder diffractometry (XRPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Assessment of enthalpy relaxation of amorphous forms was conducted using DSC in order to link the physical and chemical stability with molecular mobility. Chemical stability was studied with high-performance liquid chromatography (HPLC). Results obtained from the current study revealed that the solubility of amorphous forms prepared by both methods was enhanced compared to the crystalline form. The rank of solubility was found to be QC-big = QC-small > CM > crystalline. For the physical stability, the highest crystallization rate was observed for CM, and the slowest rate was detected for QC-big, with an intermediate rate occurring for QC-small. QC exhibited lower molecular mobility and higher chemical degradation than CM. Therefore, the current study demonstrated that QC and CM have obvious differences in both physical and chemical properties. It was concluded that care should be taken when choosing preparation methods for making amorphous materials. Furthermore, particle size, a factor that has often been overlooked when dealing with amorphous materials, was shown to have an influence on physical stability of amorphous simvastatin.     

Effects of particle size on the pharmacokinetics of puerarin nanocrystals and microcrystals after oral administration to rat

Puerarin, which is extracted from traditional Chinese medicine, is widely used in clinic in China and mainly used as a therapeutic agent to cardiovascular diseases. Owing to its poor water solubility and adverse drug reactions caused by cosolvents after intravenous administration, the development of oral formulation is urgently needed. Nowadays, nanocrystals technique has become a preferred way to develop oral dosage form. In this study, we used high pressure homogenization (HPH) to prepare puerarin nanocrystals and microcrystals with different sizes ranged from 525.8 nm to 1875.6 nm and investigated the influence of particle size on pharmacokinetics. The nanocrystals and microcrystals prepared were characterized using DLS, DSC, XRD and SEM, and we found that the crystalline state of puerarin was changed during the preparation process and the drug was dispersed into HPMC. In the pharmacokinetic study, we observed an increasing of C_max and AUC and a decreasing of CL/F with the decreasing of particle size. The AUC of the puerarin nanocrystals (525.8 nm) was 7.6-fold of that of raw puerarin suspension, with an absolute bioavailability of 21.44%. From the above results, we can conclude that nanocrystal technique is an efficient technology to improve the oral bioavailability of puerarin.     

Solid state ‘adsorption’ of fine antibiotic powders onto sorbitol: effects of particle size, state of sorbed water and surface free energy characteristics

A study has been made on the effects of the state of sorbed water, surface free energy characteristics and particle size on the ‘adsorption’ of fine antibiotic powders (ampicillin and amoxycillin trihydrates, cephalexin monohydrate and erythromycin ethylsuccinate) onto a special type of sorbitol (instant). ‘Adsorption’ was assessed by sieving before and after mixing, surface free energy characteristics were derived from contact angle measurements and state of sorbed water from sorption/desorption isotherms at different relative humidity, at 25 and 45 °C. It was found that sorbed water was externally located on sorbitol and erythromycin ethylsuccinate and internally on ampicillin, amoxycillin trihydrates and on cephalexin monohydrate, but in a different way of association as strongly bound hydrate and loosely bound hydrate water (reversible and exothermic for the latter). Erythromycin, with the highest interfacial energy value, resulted in greater extent of ‘adsorption’ than cephalexin of similar particle size, which had the lowest interfacial energy. The presence of sorbed water increased the ‘adsorption’ of ampicillin and amoxycillin trihydrates due to the contribution of capillary forces and due to their ability of hydrogen bonding at plactisized regions of sorbitol with higher moisture content and molecular mobility. The plactisizing effect of water sorbed on sorbitol is demonstrated by a logarithmic decrease of the yield pressure/elastic recovery ratio. The ‘adsorption’ of the low interfacial energy cephalexin monohydrate did not increase with the presence of water sorbed on sorbitol, presumably due to the lack of intermolecular hydrogen bonding ability, while ‘adsorption’ of erythromycin ethylsuccinate decreased, probably due to masking of the interparticle forces (van der Waal and electrostatic).     

Particle size analysis of nanocrystals: Improved analysis method

The influence of optical parameters, additional techniques (e.g. PIDS technology) and the importance of light microscopy were investigated by comparing laser diffraction data obtained via the conventional method and an optimized analysis method. Also the influence of a possible dissolution of nanocrystals during a measurement on the size result obtained was assessed in this study. The results reveal that dissolution occurs if unsaturated medium or microparticle saturated medium is used for the measurements. The dissolution is erratic and the results are not reproducible. Dissolution can be overcome by saturating the measuring medium prior to the measurement. If nanocrystals are analysed the dispersion medium should be saturated with the nanocrystals, because the solubility is higher than for coarse micro-sized drug material. The importance of using the optimized analysis method was proven by analysing 40 different nanosuspensions via the conventional versus the optimized sizing method. There was no large difference in the results obtained for the 40 nanosuspensions using the conventional method. This would have led to the conclusion, that all the 40 formulations investigated are physically stable. However, the analysis via the optimized method revealed that from 40 formulations investigated only four were physically stable. In conclusion an optimized analysis saves time and money and avoids misleading developments, because discrimination between “stable” and “unstable” can be done reliably at a very early stage of the development.     

口服胰岛素生物粘附性微球的药效与粒度的关系

目的:以脱乙酰壳聚糖为载体,制备了粒径分别为120,350和1000 nm的胰岛素生物粘附性微球并考察各类微球对四氧嘧啶糖尿病大鼠的降血糖作用.方法:采用离子趋向凝胶化方法制备了粒度不同的各类微球.光子相关光谱法及光学显微镜法测定了各类微球粒径及粒度分布.考察了处方各因素对微球粒径大小和载药量的影响及各类微球的体外释药特性.以葡萄糖氧化酶法测定血糖浓度来评价各类微球口服给药后对糖尿病大鼠的降血糖作用.结果:制备微球粒径均在所需范围,载药量分别为15.3％±1.7％(120 nm),32.4％±2.4％(350nm),53.3％±2.7％(1000 nm).粒径对微球的体外释放特性有一定的影响,0.5h后各类微球释放25％±4％(120 nm),18.3％±2.4％(350 nm),8.6％±1.3％(1000 nm).口服给药10 h后,各类微球均表现出明显的降血糖作用(P<0.05).15 h,粒径为350 nm微球所引起的降血糖作用明显高于120 nm;350 nm的微球与其它微球比,35 h后,仍具有显著的降血糖作用(P<0.01).与皮下注射相对照,口服各类微球的相对生物利用度分别是10.2％± 0.5％(120 nm),14.9％± 1.3％(350 nm),7.3％±0.8％(1000 nm).t检验结果表明,口服350 nm微球的生物利用度明显高于其它粒度的微球(P<0.05).结论:生物粘附性壳聚糖微球能够提高胰岛素的相对生物利用     

Localization and quantification of biodegradable particles in an intestinal cell model: The influence of particle size

The physicochemical parameters influencing particle crossing through the epithelial barrier have been largely studied and size has been shown as a crucial factor. Most part of this work has been done with polystyrene (PS) particles; however, few studies were conducted with well characterized biodegradable polymeric nanoparticles, more suitable for drug delivery. The aim of the present work was to study the influence of the size of well characterized biodegradable polymeric particles on cellular uptake by Caco-2 cells. Poly (d,l-lactide-co-glycolide acid) (PLGA) particles loaded with a fluorescent dye, 3,3′-dioctadecyloxacarbo-cyanine perchlorate (DiO), were prepared by the emulsion evaporation process. Five batches of particles with narrow size distribution (100, 300, 600, 1000, and 2000 nm) were produced using selective centrifugation. Surface properties (zeta potential, hydrophobicity and residual surfactant rate) were similar among all batches. Preliminary study showed that after growth and differentiation, cell counting differed from plate to plate. Therefore, a quantitative method using fluorescence spectroscopy was developed to estimate the number of particles interacting with a single cell. The results were compared to the interaction obtained with polystyrene particles, commonly used as particle model. The interaction was clearly dependant on particle size and concentration. Particles in the range of 100 nm presented a higher interaction when compared to larger particles. More than 6000 (d,l-lactide-co-glycolide acid) particles and 200,000 polystyrene particles were quantified per cell. Cellular localisation of particles by confocal microscopy showed the association of the poly (d,l-lactide-co-glycolide acid) particles with the cells. Small particles were observed intracellularly, whereas particles larger than 300 nm were associated with the apical membranes. Interestingly, some of the 100 nm PLGA particles were localized in the nuclei of the cells.     

Particle interaction of lubricated or unlubricated binary mixtures according to their particle size and densification mechanism

The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The mix of either nitrofurantoine large crystals or fine crystals with cellulose microcrystalline showed a negative interaction in all proportions, whatever particle sizes. The lubricant addition induced a positive interaction with Vivapur of greater particle size distribution (200, 102 and 101) favouring higher particle adhesivity, while it maintained unaltered that of Vivapurs of lower particle size (105 and 99). Definitely, when cohesive forces are predominant (Vivapur 105 and 99), the establishment of adhesive bonds between nitrofurantoine and Vivapur remain unnoticed; on the contrary, when cohesion bonds between microcrystalline cellulose particles are weakened by the presence of magnesium stearate, the existence of adhesion bonds between particles of different nature is in evidence, leading to a positive interaction.     

激光散射法分析异丙酚纳米乳剂的粒径大小与分布

目的制备异丙酚纳米乳剂 ,以激光散射光谱分析其粒径大小与分布 ,为微粒分散药物制剂物理稳定性的研究提供简便、快速、有效的方法。方法制备 3种处方不同 ,工艺相同的异丙酚纳米乳剂 (分别为Ⅰ、Ⅱ及Ⅲ ) ,以激光NICOMP3 80 /ZLS系统测得相应动态光散射光谱的体积为权重的重量平均粒径分布、散射强度为权重的重量平均粒径分布。结果 3个制剂动态光散射光谱有显著差别。纳米乳剂Ⅰ ,两种图谱示单峰 (davg=2 64 2nm) ;纳米乳剂Ⅱ和Ⅲ ,两种图谱示双峰 ,纳米乳剂Ⅱ中大粒子 (davg=3 1 5 5nm)占 5 4 3 % ,而小粒子 (davg=73 6nm)占 45 7% ;纳米乳剂Ⅲ示小粒子 (davg=87 1nm)占 74 9% ,而大粒子 (davg=2 3 2 7nm)占 2 5 1 %。结论 3种纳米乳剂激光光散射光谱有显著差别 ,纳米乳剂Ⅰ粒径与Ⅱ、Ⅲ相比虽稍大 ,但均匀 ,该处方制得的制剂室温放置 3年外观透明 ,物理稳定性良好     

The impact of size on tissue distribution and elimination by single intravenous injection of silica nanoparticles

Many approaches for the application of nano-sized particles to the human body as nanotechnology have been recently developed. The size of nanoparticles is related to their useful character and also plays a key role in toxicity. Since this surface area can interact with biological components of cells, nanoparticles can be more reactive in than larger particles.