Preparation and Evaluation of a Sustained-Release Formulation of Nifedipine HPMC Tablets

A nifedipine (NF) polyethylene glycol (PEG) solid dispersion was prepared. Using this solid dispersion, NF hydroxypropylmethylcellulose (HPMC) matrix tablets were prepared. Both the high-viscosity grade HPMC (Methocel K15M) and low-viscosity grade HPMC (Methocel K100) were applied in the tablets to form the matrix. The dissolution and absorption of NF from the tablet were evaluated as a formulation that had a sustained release over 24 hr. The Hixson-Crowell equation and Higuchi equation were used to investigate the dissolution mechanism, and the erosion and diffusion codependent mechanism was established. Adalat GITS 30 was used as a reference dosage form. Each beagle dog was also administered an intravenous injection to obtain the pharmacokinetics parameters. The Loo-Riegelman method was applied to study the in vitro/in vivo correlation of the tested tablets and Adalat GITS 30, and significant correlation was proved. Absolute bioavailability and comparative bioavailability of the tested tablet were studied. The results indicated that the NF HPMC tablet could be an ideal 24-hr sustained-release formulation.     

Evaluation of Compression Behavior of Paracetamol Tablets Produced with β Cyclodextrin Dispersions. Part II: Energy Distribution Study of Tablets

The compression behavior of three paracetamol/β-cyclodextrin solid dispersions (PAR/β-CD, ratio 1: 1 w/w), which differ in particle size, shape, and crystallinity, were studied using force-displacement measurements (F-D plots). The measured parameters included: effective work, expansion work, friction work, useful work, and plasticity derived from F-D plots at the tableting stage. The PAR/β-CD spray-dried solid dispersion has the best compressional behavior, compared to other dispersions (PAR/β-CD physical mixture and PAR/β-CD kneaded solid dispersion) and PAR alone. Energy distribution study also showed that β-CD has positive influence on the PAR compression characteristics.     

Evaluation of a New Cellulose Material as Binding Agent for Direct Compression of Tablets

The properties of a new microcrystalline cellulose product Emcocel^R, was compared with those of fine grade of other commercial microcrystalline cellulose, Avicel^R PH 101. The crystal structure of Avicel was noticed to be some more amorphous than that of Emcocel. Both materials were similarly composed of irregularly shaped fibrous cellulose particles. The particle size distribution was clearly larger for Emcocel than for Avicel. Emcocel contained more both very small and very large particles. The loose density was also slightly smaller for Emcocel. There was practically no difference in spesific: surface area, water content and effective density of these materials. The behaviour of both microcrystalline cellulose powders during flow and binding processes was similar. Emcocel and Emcocel were rather cohesive and only fairly flowing materials. Tablets with very advantageous strength/pressure profiles were possible to produce using plain materials and also using tablet masses containing high concentrations of acetaminophenone. According to the results of this evaluation the physical and tableting properties of a new microcrystalline cellulose material, Emcocel, resemble very closely those of Avicel PH 101. Thus neither advantage nor disadvantage is derived using Emcocel instead of Avicel PH 101 as a binding component in tablet masses.     

Formulation and Evaluation of Methocel K15M Bioadhesive Matrix Tablets

Methocel K15M is a bioadhesive polymer. Its adhesion and bioadhesion characteristics were evaluated by shear stress measurement and detachment force measurement methods, respectively. The effect of pH on adhesion was studied, and it was found that the maximum adhesion was between pH 5 and pH 6. Adhesion strength at different parts of the sheep intestine was studied; in the duodenal portion of the intestine, the adhesion was maximum. Chlorpheniramine maleate and diclofenac sodium drugs are formulated with Methocel K15M as matrix tablets. In vitro release studies revealed that some of the formulations showed initial first-order behavior followed by zero-order release behavior.     

Formulation and Evaluation of Rapidly Disintegrating Fenoverine Tablets: Effect of Superdisintegrants

The objective of this study was to formulate directly compressible rapidly disintegrating tablets of fenoverine with sufficient mechanical integrity, content uniformity, and acceptable palatability to assist patients of any age group for easy administration. Effect of varying concentrations of different superdisintegrants such as crospovidone, croscarmellose sodium, and sodium starch glycolate on disintegration time was studied. Tablets were evaluated for weight variation, thickness, hardness, friability, taste, drug content, in vitro and in vivo disintegration time, and in vitro drug release. Other parameters such as wetting time, water absorption ratio (‘R’), and drug-excipient compatibility were also evaluated. The disintegration time of the best rapidly disintegrating tablet formulation among those tested was observed to be 15.9 sec in vitro and 37.16 sec in vivo. Good correlation was observed between disintegration time and ‘R’ for each of the three superdisintegrants at the concentrations studied. Considering the ‘R’ values and disintegration time, crospovidone was significantly superior (p < 0.05) compared to the other superdisintegrants tested. Release of drug was faster from formulations containing 6% crospovidone (CP 6) compared to the marketed fenoverine (Spasmopriv®) capsules. Similarity factor ‘f₂’ (51.5) between dissolution profiles of the rapidly disintegrating tablet formulation CP 6 and the marketed formulation indicated that the two dissolution profiles were similar. Differential scanning calorimetric studies did not indicate any excipient incompatibility, either during mixing or after compression. In conclusion, directly compressible rapidly disintegrating tablets of fenoverine with lower friability, acceptable taste, and shorter disintegration times were obtained using crospovidone and other excipients at optimum concentrations.     

Design and Evaluation of a New Transdermal Formulation Containing Chlorpheniramine Maleate

The antihistamine chlorpheniramine maleate (CPM) is used for symptomatic relief of hypersensitive reactions and in pruritic skin disorders. The objective of the present study was to develop a topical formulation that contained CPM to increase patient compliance. Compliance was increased by exploiting foams that, given their application methods, avoid direct contact with the afflicted area. The study also aimed to optimize the permeability of the CPM by discerning an adequate carrier, as well as choosing the correct enhancer. The foams were formulated using aqueous solutions. In vitro studies were carried out using Franz cells with the formulations, as well as with the available pharmaceutical product Polarmin Crema®, which contains CPM. These studies showed that the permeability of the CPM in the solutions is increased more then 100 times with respect to the water-in-oil emulsion Polarmin Crema. In particular, the highest permeability was obtained using limonene as an enhancer.     

Formulation and Evaluation of Mucoadhesive Tablets Containing Eugenol for the Treatment of Periodontal Diseases

Eugenol is the principle chemical constituent of clove oil and has been used to cure dental problems for ages. Eugenol is an integral part of the dentist's kit due to its analgesic, local anesthetic, anti‐;inflammatory, and antibacterial effects. It is used in the form of a paste or mixture as dental cement, filler, and restorative material. This study reports the development and evaluation of controlled‐release mucoadhesive tablets for gingival application, containing eugenol, which are prepared by taking carbopol 934 P and Hydroxypropyl methylcellulose (HPMC) K4M in the ratio of 1:2, 1:1, and 2:1. Incorporation of eugenol (10 mg) in a mucoadhesive formulation provides controlled release for a period of 8 hours, which is advantageous over conventional use. In vitro mucoadhesion measured as detachment force in grams and the formulations show good correlation in vivo. The release study indicates that increase in carbopol increases the release rate of eugenol from the formulation whereas HPMC retards it. Increased in vitro bioadhesion is related to HPMC content of the formulation. The release kinetics of eugenol in vitro correlates with the in vivo results. This indicates the increased potential of eugenol as antibacterial, local analgesic, and anaesthetic treatment.     

Communications Evaluation of Egg Albumin as a Filler for Prolonged Release Direct Compressed Tablets

Direct compressed tablets for drugs of different physico-chemical properties were prepared using egg albumin as tablet filler. The prepared tablets at different drug:egg albumin ratios as well as the powder blends used for the preparation of the tablets were evaluated. The drug dissolutions from the egg albumin tablets were slow and different release profiles were obtained depending on the type of the drug. The release kinetics from the albumin matrix were tested for different models and were found to be anomalous resembling release of drugs from swellable type of matrices. In order to elucidate the release mechanism, the interaction of drugs with egg albumin was examined by thermal analysis. In most cases release retardation was increased with the increase of egg albumin matrix density. In case of meclizine-HCl the release was not depending on the egg albumin matrix density and it was believed that the rate determining step for its release is drug solubility and/or dissociation of the drug-egg albumin complex.     

Characterization and Performance of a New Direct Compression Excipient for Chewable Tablets: Xylitab®

Xylitab® is a commercially available direct compression form of xylitol. Two grades of this material, Xylitab 200 and Xylitab 100, were evaluated for compaction, flow, lubrication requirements, and dilution potential. As expected, the products required lubrication for tableting, and a level of 0.5% magnesium stearate and 0.5% stearic acid was found to give the best performance. Compaction profiles were generated using both an instrumented single-punch press and a rotary tablet press. Tablets up to hardness values of 20 Kp were obtained on the single-punch press; the maximum hardness values on the rotary press was 11 Kp. Flow behavior on the tablet presses was excellent as shown by tablet weight uniformity data with less than 1% RSD values. Further evaluation by Heckel analysis showed that both products exhibit brittle and viscoelastic behavior, and undergo elastic recovery primarily in the die. To test dilution potential, powdered acetaminophen was selected as a severe test material. Under these conditions, 20% drug still produced an acceptable tablet, but hardness values were reduced as expected. With a directly compressible grade of acetaminophen, a complete chewable formulation was successfully produced using Xylitab 200 as the main direct compression excipient and sweetening agent. Xylitab exhibits acceptable properties as a direct compression chewable tablet excipient and warrants further study.     

水溶性壳低聚糖快速制备的方法及其性能表征

针对天然壳聚糖不溶于水的特点,采用微波辅助下的H_2O_2/UV体系快速氧化降解壳聚糖,制备得到不同低分子质量的水溶性壳低聚糖,并对壳低聚糖的相对分子质量、分子结构和水溶性进行表征。实验结果表明,天然壳聚糖在微波辅助下的H_2O_2/UV体系中5 min内发生快速降解,制备得到的壳低聚糖在较宽的p H值范围内都具有良好的水溶性。FTIR结果表明,水溶性壳低聚糖的化学结构和功能基团与壳聚糖原料一致;XRD结果表明H_2O_2会对壳聚糖的结晶结构造成破坏,从而使壳低聚糖的水溶性得到提升;TG结果表明水溶性的壳低聚糖结晶区被破坏后,热稳定性变差。     

The New Method of Semiconductor Devices Production by Wafers Direct Bonding

Problems of a new technological process of multilayer silicon structure formation by direct bonding of silicon wafers (SDB) are reviewed. The main accent is made on the consideration of possible mechanisms of semiadhesive bonding of silicon surfaces at low-temperature and high-temperature steps of the bonding process. Issues regarding the quality of multilayer structures such as absence of voids, crystal structure peculiarities of the bonding interface, and electrical properties of the device layers are presented. Examples of applications of the SDB multilayer structures in device fabrication are shown. The review includes both the consideration of principal reports on the subject and the author's experimental results.     

Comparative Evaluation of Certain Excipients and their Binary Blends for Direct Compression Oxytetracycline Hydrochloride Tablets

Abstract

Five direct compression excipients as well as their binary blends in ratios of 1:1, 1:3 and 3:1 were comparatively evaluated to compress oxytetracycline hydrochloride into tablets. With respect to the mechanical properties of the produced tablets, Avicel PH101, Celutab and STAR-x1500 in this order, were the most suitable single excipients for the production. The results showed that the incorporation of a second excipient in the formulation changes the physical standards of the produced antibiotic tablets. It was found that not only the type of the incorporated excipient is effective but also, its concentration in the formula. The investigation proved that Avicel/STAR-x1500 blends in all different ratios followed by some blends of celutab with Avicel or STAR-x1500 were the best blended excipients to produce satisfactory antibiotic tablets.     

Evaluation of a New Fine Particulate Cellulose as a Direct Compression Tablet Aid

Abstract

A new grade of α-cellulose, composed of a mixture of amorphous and crystalline cellulose was evaluated in this preliminary study for its potential as an inert direct compression tablet vehicle. Though not a micro-crystalline cellulose, this product, identified as EGC, possesses the tabletting characteristics of micro-crystalline cellulose. It is prepared by a physicochemical procedure that does not require severe heat or acid treatment but yields a product which is white, fine granular, free-flowing and highly compressible.     

Lubricants as a Formulation Factor Affecting In Vitro Properties of Double Compressed Tablets

Abstract

The effect of some lubricants and their concentrations on the in-vitro properties of aspirin tablets as a model of tablets prepared by double compression was studied. The formulated tablets were evaluated using the U.S.P XX official tests and some other selected non-official tests. These tests include: uniformity of weight, uniformity of content, disintegration, dissolution, hardness, friability and thickness. The obtained results showed that all the prepared formulae fulfilled the requirements of such tests. Talc at a concentration of 3% w/w was found to be the most suitable lubricant for the formulation of aspirin tablets. On the other hand, magnesium stearate was found to be the worst lubricant in this study.     

Direct Measurement of Rotation by a Laser Speckle Method

The laser speckle pattern produced by the coherent illumination of a small circular portion of a doubly exposed photograph contains enough information to reveal not only the displacement but also the rotation of a rigidly moving two-dimensional field. The displacement of the field is contained in the resulting parallel speckle fringe spacing in the usual way. The magnitude of the rotation of the field, however, may be determined by measuring the radius of the circular region within which these displacement speckle fringes appear. Photographs and analyses of the resulting speckle patterns are presented. Non-rigid two-dimensional motion and its relation to incompressible fluid flow is also discussed.     

Formulation and Evaluation of Methotrexate Niosomes

Abstract

Methotrexate was encapsulated in niosomes prepared using Tweens and Spans. The size distribution, entrapment efficiency, pharmacokinetics and effect on tumour remission of mice transplanted with S-180 Sarcoma were evaluated. Niosomes prepared with Span 60 gave promising results.     

Formulation and Evaluation of Methotrexate Niosomes

Methotrexate was encapsulated in niosomes prepared using Tweens and Spans. The size distribution, entrapment efficiency, pharmacokinetics and effect on tumour remission of mice transplanted with S-180 Sarcoma were evaluated. Niosomes prepared with Span 60 gave promising results.     

Formulation and Release Kinetics of Sustained Release Phenylpropanolamine Hydrochloride Granules and Tablets

Abstract

Sustained release phenylpropanolamine hydrochloride (PPH) granules and tablets were prepared using HPMC, HPMC and SCMC, Eudragit RS, Eudragit RS+L or HPMC + Eudragit RS matrices. The release pattern of PPH from the prepared granules and tablets was found to be in the following order HPMC > HPMC + SCMC > RS > RS + 1> HPMC + RS. The results revealed that, although the drug concentration was kept constant in all the prepared granules and tablets, the drug release from these formulations was clearly different and depends mainly on the type of matrix used. The presence of Eudragit L with Eudragit RS and Eudragit RS with HPMC resulted in a marked decrease in the drug release compared with that obtained from the matrix containing HPMC or Eudragit RS alone. The release data of PPH from the prepared granules and tablets were treated mathematically according to zero order, first order, Langenbuchar, modified Langenbucher and Higuchi models. The results revealed that no one model was able adequately to describe the drug release profiles from these formulations. In-vivo studies in human volunteers showed that, the peak urinary excretion of PPH occurred over a sustained period from 2 to 6.5 hr in case of HPMC + SCMC tablets and from 2 to 10 hr in case of either RS+L or HPMC + RS tablets.     

In-Vivo Evaluation of a Bioadhesive Containing Indomethacin Tablets

The relative bioavailability of a bioadhesive containing, directly compressed, tablet formulation against the commercial indomethacin capsules “Indocid, MSD” has been investigated in dogs. The tablets showed a prolongation of the time to reach maximum concentration to 3 hours compared to 2 hours in capsules. They also showed 39% and 184% increase in maximum and minimum plasma concentration, respectively. The relative bioavailability of the tablets is 152% compared to capsules where the tablets showed a mean area under the plasma concentration-time curve of 26 ug.hr/ml compared to 17 ug.hr/ml for capsules.