Theoretical and experimental investigations on the morphology of pharmaceutical crystals

We investigated the morphologies of three polymorphs of 1,3-di(cyclopropylmethyl)-8-aminoxanthine, a compound of pharmaceutical importance. We compared the experimental morphologies with those predicted by theoretical methods. We also predicted the elastic constants of the three polymorphs. These results are used to help assess the stabilities of the three polymorphs and compare the abilities of theoretical methods to reproduce experimental morphologies.     

Theoretical and experimental investigations on the size of alginate microspheres prepared by dropping and spraying

In order to produce functional microspheres with different ranges of sizes for various applications, the size of alginate droplets prepared by dropping and spraying was studied. It was shown that the mean diameter could be controlled by liquid flow velocity and applied voltage as operating parameters using a conventional dropping and an electrostatic dropping method, separately. The formation mechanism of alginate droplets could be categorized into two different modes: Dripping mode and jetting mode. By employing an effective force analysis, the diameters in each modes showed to be well agreed with the numerical simulation within 7% deviations. It was testified that the initial amount of surface charges had a high impact on droplet diameter and the liquid flow velocity played a more important role on mean diameter of alginate droplets by electrostatic dropping method in dripping mode than in jetting mode. Then, an empirical equation and a semi-empirical model were used to simulate the diameter of droplets obtained by spraying and spraying with electrostatic field (SEF) method, respectively. The decrease in diameter was more sensitive to the increase of gas flow rate than to the decrease of liquid flow rate, and the results of two models fitted well with experimental values. The simulations showed that SEF yielded a 20% lower on droplet diameter than simple spraying method.     

Theoretical and experimental investigations on the size of alginate microspheres prepared by dropping and spraying

In order to produce functional microspheres with different ranges of sizes for various applications, the size of alginate droplets prepared by dropping and spraying was studied. It was shown that the mean diameter could be controlled by liquid flow velocity and applied voltage as operating parameters using a conventional dropping and an electrostatic dropping method, separately. The formation mechanism of alginate droplets could be categorized into two different modes: Dripping mode and jetting mode. By employing an effective force analysis, the diameters in each modes showed to be well agreed with the numerical simulation within 7% deviations. It was testified that the initial amount of surface charges had a high impact on droplet diameter and the liquid flow velocity played a more important role on mean diameter of alginate droplets by electrostatic dropping method in dripping mode than in jetting mode. Then, an empirical equation and a semi-empirical model were used to simulate the diameter of droplets obtained by spraying and spraying with electrostatic field (SEF) method, respectively. The decrease in diameter was more sensitive to the increase of gas flow rate than to the decrease of liquid flow rate, and the results of two models fitted well with experimental values. The simulations showed that SEF yielded a 20% lower on droplet diameter than simple spraying method.     

Formulation development and optimization of bilayer tablets of aceclofenac

Objective: The objective of the present study was to develop bilayer tablets of aceclofenac that are characterized by initial burst drug release followed by sustained release of drug. Methods: The fast-release layer of the bilayer tablet was formulated using microcrystaline cellulose (MCC) and HPMC K4M. The amount of HPMC E4M (X(1)) and MCC (X(2)) was used as independent variables for optimization of sustained release formulation applying 3(2) factorial design. Three dependent variables were considered: percentage of aceclofenac release at 1 h, percentage of aceclofenac release at 12 h, and time to release 50% of drug (t(50%)). The composition of optimum formulation of sustained release tablets were employed to formulate double layer tablets. Results: The results indicate that X(1) and X(2) significantly affected the release properties of aceclofenac from sustained release formulation. The double layer tablets containing fast-release layer showed an initial burst drug release of more than 30% of its drug content during first 1 h followed by sustained release of the drug for a period of 24 h. Conclusion: The double layer tablets for aceclofenac can be successfully employed as once-a-day oral-controlled release drug delivery system characterized by initial burst release of aceclofenac for providing the loading dose of drug.     

Design and evaluation of bilayer floating tablets of captopril

The objective of the present investigation was to develop a bilayer-floating tablet (BFT) for captopril using direct compression technology. HPMC, K-grade and effervescent mixture of citric acid and sodium bicarbonate formed the floating layer. The release layer contained captopril and various polymers such as HPMC-K15M, PVP-K30 and Carbopol 934p, alone or in combination with the drug. The floating behavior and in vitro dissolution studies were carried out in a USP 23 apparatus 2 in simulated gastric fluid (without enzyme, pH 1.2). Final formulation released approximately 95% drug in 24 h in vitro, while the floating lag time was 10 min and the tablet remained floatable throughout all studies. Final formulation followed the Higuchi release model and showed no significant change in physical appearance, drug content, floatability or in vitro dissolution pattern after storage at 45 degrees C/75% RH for three months. Placebo formulation containing barium sulphate in the release layer administered to human volunteers for in vivo X-ray studies showed that BFT had significantly increased the gastric residence time.     

Formulation development and optimization of bilayer tablets of aceclofenac

Objective: The objective of the present study was to develop bilayer tablets of aceclofenac that are characterized by initial burst drug release followed by sustained release of drug.

Methods: The fast-release layer of the bilayer tablet was formulated using microcrystaline cellulose (MCC) and HPMC K4M. The amount of HPMC E4M (X₁) and MCC (X₂) was used as independent variables for optimization of sustained release formulation applying 3² factorial design. Three dependent variables were considered: percentage of aceclofenac release at 1 h, percentage of aceclofenac release at 12 h, and time to release 50% of drug (t_50%). The composition of optimum formulation of sustained release tablets were employed to formulate double layer tablets.

Results: The results indicate that X₁ and X₂ significantly affected the release properties of aceclofenac from sustained release formulation. The double layer tablets containing fast-release layer showed an initial burst drug release of more than 30% of its drug content during first 1 h followed by sustained release of the drug for a period of 24 h.

Conclusion: The double layer tablets for aceclofenac can be successfully employed as once-a-day oral-controlled release drug delivery system characterized by initial burst release of aceclofenac for providing the loading dose of drug.     

Theoretical investigations on the structure and potential binding sites of antineoplaston A10 and experimental findings

The essential biological importance of antineoplastons has motivated the present theoretical and experimental studies on the structure and potential binding sites of Antineoplaston A10, 3-phenylacetylamino-2,6-piperidinedione. Semi-empirical molecular orbital calculations SCF-LCAO-MO were performed using the MNDO method. The calculated molecular geometry of A10 is in very good agreement with the recently obtained X-ray structure of synthetic A10. Experimental investigations of the Raman spectra of A10 and its N,N-dideuterated derivative confirm the theoretical predictions concerning the structure and hydrogen bonding of A10. Analysis of calculated charge distribution reveals that the negative charges are localized on the ring nitrogen and on the exocyclic oxygen atoms of A10 and are similar to the corresponding charges computed for some pyrimidine bases. This indicates that Antineoplaston A10 may have similar binding sites. It is concluded that the mechanism of action of Antineoplaston A10 may in part be related to its structural and chemical resemblance with deoxythymidine and uridine. A10 may act as a nucleoside antagonist and interact very closely with adenosine units in nucleic acids and enzymes, which may interfere with protein synthesis in neoplastic cells.     

替米沙坦氨氯地平双层片的制备及体外释放度研究

目的制备复方替米沙坦氨氯地平片并考查其体外释放度。方法采用直压法制备替米沙坦氨氯地平片;建立同时测定替米沙坦、氨氯地平含量的高效液相色谱法;以水、pH2.0盐酸溶液、pH6.8、pH7.4磷酸盐缓冲液为溶出介质,桨法测定本品释放度,并与参比制剂Twynst进行比较。结果释放曲线经相似因子判断,与参比制剂相似。结论本品处方工艺稳定,重现性好,体外累积释放度符合要求。     

Influence of compaction properties and interfacial topography on the performance of bilayer tablets

Bilayer tablets are generating great interest recently as they can achieve controlled delivery of different drugs with pre-defined release profiles. However, the production of such tablets has been facing great challenges as the layered tablets are prone to delaminate or fracture in the individual layers due to insufficient bonding strength of layers and adhesion at the interfaces. This paper will provide an insight into the role of interfacial topography on the performance of the bilayer tablets. In this study, two widely used pharmaceutical excipients: microcrystalline cellulose and lactose were investigated. Bilayer tablets were manufactured with a range of first and second layer compression forces. A crack of known dimensions was introduced at the interface to investigate the crack propagation mechanisms upon axially loading the bilayer tablet, and to determine the stress intensity factor (K(I)) of the interface (will be discussed in a separate paper). The results indicated that a strong dependency of the strength of bilayer tablets and mode of crack propagation on the material and compaction properties. The results showed that the strength of bilayer tablets increased with the increase of interfacial roughness, and the first layer and second layer forces determined the magnitude of interfacial roughness for both plastic and brittle materials. Further, the results also indicated that layer sequence and compaction forces played a key role in influencing the strength of the bilayer tablets. For the same (first and second layer) force combination, interfacial strength is higher for the tablets made of brittle material in the first layer. It was observed that interfacial strength decreased with the increase of lubricant concentration. The studies showed that the effect of lubricant (i.e. reduction in compact strength with the increase of lubricant concentration) on the strength of compacts is higher for tablets made of plastic material as compared to the tablets made of brittle material.     

Design and evaluation of sustained release bilayer tablets of propranolol hydrochloride

The objective of the present research was to develop a bilayer tablet of propranolol hydrochloride using superdisintegrant sodium starch glycolate for the fast release layer and water immiscible polymers such as ethylcellulose, Eudragit RLPO and Eudragit RSPO for the sustaining layer. In vitro dissolution studies were carried out in a USP 24 apparatus I. The formulations gave an initial burst effect to provide the loading dose of the drug followed by sustained release for 12 h from the sustaining layer of matrix embedded tablets. In vitro dissolution kinetics followed the Higuchi model via a non-Fickian diffusion controlled release mechanism after the initial burst release. FT-IR studies revealed that there was no interaction between the drug and polymers used in the study. Statistical analysis (ANOVA) showed no significant difference in the cumulative amount of drug release after 15 min, but significant difference (p < 0.05) in the amount of drug released after 12 h from optimized formulations was observed.     

Theoretical and experimental investigations on miconazole/cyclodextrin/acid complexes: molecular modeling studies

The inclusion of miconazole into cyclodextrin cavity has been demonstrated by different authors. Preliminary studies have shown which fragment of the molecule is involved in the inclusion. In the present study, AM1 approximate molecular orbital calculations have been performed on several cyclodextrins complexes (betaCD, HPbetaCD and HPgammaCD) with miconazole and acidic compounds (maleic, fumaric and L-tartaric acids) as partners. For all the binary complexes, the inclusion of the dichlorobenzene-CH(2)-O-group leads to the most stable complex. For the ternary complexes, depending on their conformation and/or their structures, the acids can either stabilize or destabilize the complex. All the theoretical results were in good agreement with experimental data of miconazole inclusion yields into cyclodextrins. This work clearly demonstrates that the structure of both cyclodextrin and acid plays a key-role in the formation of inclusion complexes.     

效应面法优化尼美舒利双层缓释片处方

采用正交设计及星点设计-效应面法对尼美舒利双层缓释片处方进行优化。优化后的处方如下：（Ⅰ）速释层：尼美舒利,50 mg;乳糖,92 mg;淀粉,22 mg;CCMC-Na,14 mg;PVP K30,1 mg;微粉硅胶,1 mg;硬脂酸镁,0.9 mg;氧化铁红,0.1 mg;（Ⅱ）缓释层：尼美舒利,150 mg;HPMC K100LV,26 mg;HPMC K4M,33 mg;乳糖,54 mg;PVP K30,1 mg;微粉硅胶,1 mg;硬脂酸镁,0.9 mg。优化后的处方在初期药物快速释放（10 min释放15%）,后期缓慢释放持续一段时间（16 h）,具有双相释放特征,且放置6个月后无明显变化。     

褪黑素双层控释片制备及其在Beagle犬体内的药动学

目的：研制褪黑素双层控释片,并研究其药动学。方法：以羟丙甲基纤维素、硬脂酸为骨架材料,采用固体分散技术和双层压片工艺,制备褪黑素双层控释片。6只Beagle犬随机交叉单剂灌服褪黑素双层控释片(6 mg)或参比制剂(3 mg),以高效液相色谱法测定血浆中褪黑素浓度,3P97程序推算药动学参数。结果：灌服受试制剂和参比制剂后,t_((1/2)ke)分别为(3．3±s0．9)和(1．2±0．5)h,c_(max)分别为(8±5)和(11±4)μg·L~(-1),t_(max)分别为(1．0±0．4)和(0．50±0．20)h,AUC_(0-(?))分别为(38±16)和(25±8)μg·h·L~(-1)。结论：研制的褪黑素双层控释片具有速释和缓释特性。     

格列吡嗪双层渗透泵片在比格犬体内的药动学

目的考察格列吡嗪双层渗透泵片在比格犬体内的药动学过程,评价其生物等效性及体内体外相关性。方法建立格列吡嗪比格犬血浆样品的UPLC/MS/MS测定方法,以市售格列吡嗪控释片(瑞易宁)为参比制剂,对自制格列吡嗪控释片进行了比格犬体内药动学研究。结果建立了测定格列吡嗪UPLC/MS/MS方法,方法灵敏度高,分析速度快。自制格列吡嗪控释片中格列吡嗪的相对生物利用度为(85.37±26.69)%。结论受试制剂和参比制剂生物不等效,但体内外相关性较好。     

洛索洛芬钠双层缓释片的研制和体外释放特性研究

目的：研制洛索洛芬钠双层缓释片并考察其体外释药特性。方法：以两种不同处方作湿法制粒,压制双层片,用高效液相色谱法测定洛索洛芬钠的释放度.结果与结论：洛索洛芬钠双层缓释片的释药曲线可用Higuchi方程或Peppas方程拟合,可维持12h持续释放达到设计要求.     

采用相似因子法评价不同因素对复方二甲双胍格列吡嗪双层缓释片体外释放的影响

目的考察不同因素对复方二甲双胍格列吡嗪双层缓释片(BT)体外释放的影响。方法采用相似因子法进行考察。结果各种因素对二甲双胍释放速率影响不大;HPMC的黏度、用量、填充剂的种类和搅拌速度对格列吡嗪释放速率有明显影响,填充剂的用量对格列吡嗪释放速率影响较小。结论相似因子法适合于缓控释制剂体外释放的评价。     

基于QbD理念的对乙酰氨基酚双释双层片制备工艺的设计及优化

目的：基于"质量源于设计"（QbD）理念设计并优化对乙酰氨基酚双释双层片（简称为"双层片"）的制备工艺。方法：采用Plackett-Burman考察法确定双层片制备工艺的关键工艺参数（CPPs）;采用Box-Behnken响应面设计,以缓释层的释放度、速释层的溶出度作为关键质量属性（CQAs）,优化双层片的最佳处方、工艺参数;在二次多项式回归模型的基础上建立双层片工艺设计空间,并加以验证。结果：对乙酰氨基酚双层片最佳工艺为：崩解剂量所占比例为9.5%,制粒目数为22目,缓材比例为5∶1;设计空间以Overlay plot方式展示,并加入95%置信区间,设计空间工艺稳定可靠。结论：所制定的工艺对乙酰氨基酚双释双层片制备工艺简单,制剂稳定,适合大工业生产。     

Biochemical investigations into the mode of action of trazodone

Trazodone is an antidepressant drug with well established clinical efficacy in the treatment of depressive disorders, in addition to a marked anxiolytic activity. In contrast to tricyclic, and certain other antidepressant drugs, trazodone has been shown to have no effects on noradrenaline (NA) reuptake mechanisms. Whereas trazodone is a weak inhibitor of the in vitro uptake of [³H]-5-hydroxy-tryptamine (5-HT) into rat occipital cortex synaptosomes, a potent effect shown by this compound is the in vivo occupation of serotonergic [³H]-spiperone binding sites in the mouse frontal cortex; an activity shared by putative 5-HT antagonists and several other antidepressant drugs. The 5-HT antagonist activity of trazodone has been behaviourally verified by the antagonism of the serotonergic head-twitch response elicited by the 5-HT agonist, MK, 212, in mice. Trazodone also interacts with alpha-noradrenergic receptors as assessed by in vitro receptor binding experiments with the radioligands [³H]-WB 4101 and [³H]-dihydroergocryptine (DHE). Ex vivo experiments indicate that, after oral administration to rats, trazodone occupies cortical alpha₂ receptor sites, but with a lower potency than either mianserin or yohimbine. Experiments with superfused rat occipital cortex mini-slices have shown that trazodone can enhance the potassium stimulated and spontaneous efflux of preloaded [³H]-NA. The combination of alpha₂ antagonism and NA releasing properties, in the absence of reuptake inhibition, may be associated with the antidepressant activity of this drug, whereas the potent 5-HT antagonist activity may explain the anxiolytic effects. Finally, trazodone has been found to be devoid of muscarinie receptor affinity as measured by [³H]-quinuclidinyl benzilate (QNB) radioreceptor assays in accord with clinical observation of the absence of anticholinergic side-effects.     

Theoretical and experimental investigations of organic acids/cyclodextrin complexes and their consequences upon the formation of miconazole/cyclodextrin/acid ternary inclusion complexes

(1)H NMR spectrometry, FT-IR spectroscopy, as well as molecular modeling at the AM1 level and normal mode analysis were used to characterise the interactions and the formation of inclusion complexes between three organic acids: maleic, fumaric, L-tartaric acids and betaCD. In aqueous medium, the complexation was confirmed by (1)H NMR spectroscopy using two-dimensional technique. The stable geometries of the complexes were determined by molecular modeling. Experimental infrared frequencies were assigned on the base of the vibrational normal mode calculation at the fully optimized geometry for the inclusion complexes. All the results point out the presence of stable inclusion complexes between acids and betaCD at the solid state. These results show the double role of the acid. Correlated with the theoretical and experimental data previously obtained for the miconazole/CD/acids complexes, in function of both acids and CDs structures, the acids can either stabilize the complexes by formation of a multicomponent complex or form acid/CD inclusion complexes, hindering the guest inclusion.     

Metabonomic investigations into hydrazine toxicity in the rat

The systemic biochemical effects of oral hydrazine administration (dosed at 75, 90, and 120 mg/kg) have been investigated in male Han Wistar rats using metabonomic analysis of (1)H NMR spectra of urine and plasma, conventional clinical chemistry, and liver histopathology. Plasma samples were collected both pre- and 24 h postdose, while urine was collected predose and daily over a 7 day postdose period. (1)H NMR spectra of the biofluids were analyzed visually and via pattern recognition using principal component analysis. The latter showed that there was a dose-dependent biochemical effect of hydrazine treatment on the levels of a range of low molecular weight compounds in urine and plasma, which was correlated with the severity of the hydrazine induced liver lesions. In plasma, increases in the levels of free glycine, alanine, isoleucine, valine, lysine, arginine, tyrosine, citrulline, 3-D-hydroxybutyrate, creatine, histidine, and threonine were observed. Urinary excretion of hippurate, citrate, succinate, 2-oxoglutarate, trimethylamine-N-oxide, fumarate and creatinine were decreased following hydrazine dosing, whereas taurine, creatine, threonine, N-methylnicotinic acid, tyrosine, beta-alanine, citrulline, Nalpha-acetylcitrulline and argininosuccinate excretion was increased. Moreover, the most notable effect was the appearance in urine and plasma of 2-aminoadipate, which has previously been shown to lead to neurological effects in rats. High urinary levels of 2-aminoadipate may explain the hitherto poorly understood neurological effects of hydrazine. Metabonomic analysis of high-resolution (1)H NMR spectra of biofluids has provided a means of monitoring the progression of toxicity and recovery, while also allowing the identification of novel biomarkers of development and regression of the lesion.