Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Tablets”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,549 records · Page 86Linked to original sources
PubMed2004

Influence of hydroxypropyl-beta-cyclodextrin complexation on piroxicam release from buccoadhesive tablets.

Interaction of piroxicam (PX) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) was investigated in solution and in the solid state. Solubility studies demonstrated the formation of the PX-HPbetaCD inclusion complex with 1:1 stoichiometry. Equimolecular PX-HPbetaCD solid systems were prepared and characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffractometry. Modification of the release of a sparingly water-soluble drug, PX, from hydrophilic matrices using cyclodextrin complexation was evaluated. The buccoadhesive controlled release tablets for the delivery of PX were prepared by direct compression of hydroxypropylmethyl cellulose (HPMC) and Carbopol 940 (C940), which showed superior bioadhesion properties compared to HPMC. The tablets were evaluated for their dissolution, swelling and mucoadhesive properties. The in vitro release results demonstrated that matrix tablets containing the PX-HPbetaCD solid complex displayed faster PX release compared to those containing a physical mixture or "free" drug. Differences in release rates of PX from the tablets could be attributed to the presence of the polymers and to cyclodextrin complexation. The effect of the polymers on PX release can affect the drug solubility (complexation) and polymer water uptake (swelling). Higher polymer water uptake may result in higher drug solubility and diffusivity in a hydrated polymeric environment. Drug complexation affected also its diffusivity through the semipermeable membrane.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2004

Compression behaviour and tablet-forming ability of spray-dried amorphous composite particles.

The aim of this study was to investigate the compression behaviour and tablet-forming ability of spray-dried amorphous two- and three-component composite particles. Particles of lactose alone, two-component particles of lactose and PVP, and three-component particles of lactose, PVP and a small amount of polysorbate 80 were prepared by spray-drying. Two qualities of PVP with different molecular weights were used for the preparation of both types of particles. The particles were characterised with respect to permeametry surface area, moisture content, particle and bulk density, glass transition and crystallisation temperature, and heat of crystallisation. The tablet tensile strength of the different particles formed at a series of applied pressures was determined and compression parameters were derived from the Heckel and Kawakita equations. The presence of PVP gave particles that were less prone to deform permanently during compression while the presence of surfactant gave particles that were less able to form tablets. In conclusion, the compression behaviour and tablet-forming ability of spray-dried amorphous lactose can be modulated by the addition of stabilising polymers or surfactants to the spray feed solution.

Compressive Strength↗
PubMed2005

A simple predictive model for the tensile strength of binary tablets.

The tensile strength of tablets of single-component powders, such as microcrystalline cellulose (MCC), hydroxypropylmethyl cellulose (HPMC) and starch, and binary mixtures of these powder were measured at various relative densities. It was found that the tensile strength of tablets of powder blends was primarily dependent upon relative density but was independent of the tablet dimensions and compaction kinematics. It was found that the logarithm of tensile strength was proportional to the relative density. A simple model, based upon Ryshkewitch-Duckworth equation that was originally proposed for porous materials, has been developed in order to predict the relationship between the tensile strength and relative density of binary tablets based on the properties of the constituent single-component powders. The validity of the model has been verified with experimental results for various binary mixtures. It has demonstrated that the proposed model can well predict the tensile strength of binary mixtures based upon the properties of single-component powders, such as true density, and the concentrations.

Cellulose↗
PubMed2006

Tensile stresses generated in pharmaceutical tablets by opposing compressive line loads.

The distribution of tensile stress, across the splitting plane, has been investigated for the case when circular and square tablets are subjected to opposing compressive line loads acting in the through thickness direction. This type of loading is referred to in the paper as axial compression. Analytical solutions for the two-dimensional problem of a rectangular strip have been used to investigate the variation of stress in the through thickness direction and to consider the effects of load spreading. Three-dimensional finite element analysis has been used to investigate the variation in stress across the diameter, or breadth, of the tablets. It is shown that the magnitude of the tensile stress varies significantly throughout and that load spreading has an important influence on the stress distribution in the through thickness direction. Experiments have been carried out with microcrystalline cellulose (Avicel PH102) material for circular and square tablets to determine their breaking loads when subjected to axial compression and diametral compression. The experimental results show higher breaking loads for the case of axial compression. It is concluded that the platen contact width must be known in order to evaluate the exact value of the tensile strength of the tablet material when applying this test procedure.

Algorithms↗
PubMed2004

Measurement of density variations in tablets using X-ray computed tomography.

In this paper the application of X-ray computed tomography (CT) to measure the material density distribution in pharmaceutical tablets is discussed. X-ray CT is a non-destructive inspection technique which provides cross-sectional images in different planes through a component. The CT image values provide information on the local X-ray attenuation coefficients. For a particular material and X-ray energy, X-ray attenuation is approximately proportional to material density. Determination of quantitative density distributions requires consideration of non-linear instrumental effects including scatter and "beam hardening". Density maps in tablets manufactured under controlled conditions are presented. The results are discussed with reference to the local properties of the material within the tablet and the tablet design features.

Cellulose↗
PubMed2005

Determination of the in vitro disintegration profile of rapidly disintegrating tablets and correlation with oral disintegration.

The assessment of the in vitro disintegration profile of rapidly disintegrating tablets (RDT) is very important in the evaluation and the development of new formulations of this type. So far neither the US Pharmacopoeia nor the European Pharmacopoeia has defined a specific disintegration test for RDT; currently, it is only possible to refer to the tests on dispersible or effervescent tablets for the evaluation of RDT's disintegration capacity. In the present study, we have evaluated the disintegration profile of RDT manufactured by main commercialised technologies, using the texture analyser (TA). In order to simulate as much as possible the oral disintegration of these dosage forms, a new operating structure was developed. This structure mimics the situation in the patient's mouth and provides a gradual elimination of the detached particles during the disintegration process. The obtained time-distance profiles or disintegration profiles enabled the calculation of certain quantitative values as the disintegration onset (t1) and the total disintegration time (t2). These values were used in the characterisation of the effect of test variables as the disintegration medium and temperature on the disintegration time of RDT. Moreover, the oral disintegration time of the same products was evaluated by 14 healthy volunteers. Results obtained when artificial saliva at 37 degrees C was employed as disintegration medium were used to correlate the in vitro (t2) and oral disintegration times. Excellent correlation was found and in addition, we were able to achieve a qualitative measure of the mouthfeel by comparing the thickness of the tablets and the penetration distance obtained from the disintegration profile. This method also permitted the discrimination between different RDT, where differences in the disintegration mechanism were reflected on the disintegration profile achieved for each tablet.

Administration, Oral↗
PubMed2005

Glycerin fatty acid esters as a new lubricant of tablets.

Lubrication properties were compared among glycerin fatty acid esters (Poem TR-FB and Poem TR-HB), magnesium stearate (Mg-St), and a sucrose fatty acid ester (RYOTO SUGAR ESTER S-370F: SSE). Granules containing 50% acetaminophen were prepared, and improvements in their fluidity by the lubricants were compared. The lubricant effects of TR-FB and HB during tablet punching (pressure transmission ratio, ejection force) were similar to those of Mg-St and were better than those of SSE. When the lubricant content, mixing time, and tabletting pressure were changed, TR-FB and TR-HB provided better tablet hardness than Mg-St. TR-FB and TR-HB made tablets more disintegratable than Mg-St. When the effects of these lubricants on the stability of acetylsalicylic acid (ASA) were compared, Mg-St promoted its hydrolysis, but TR-FB or TR-HB did not affect its stability.

Esters↗
PubMed2005

Preparation, characterization, and tableting of a solid dispersion of indomethacin with crospovidone.

A significant problem with solid dispersion (SD) systems is the difficulty in preparing dosage forms. This difficulty can be overcome using crospovidone (CrosPVP) as a carrier. A powder SD of indomethacin (IM) with CrosPVP was prepared using mechanical mixing followed by heating to temperatures below the melting point. IM and CrosPVP interacted to produce IM in an amorphous state when its concentration was <40%. The solubility of IM was improved about fourfold compared to IM crystal. The SD had good fluidity, and tablets were prepared by direct compression. Tablets with small weight variation and acceptable hardness were obtained using only 1% of magnesium stearate as excipient. The dissolution of IM from tablets was similar to that of SD powder because CrosPVP, a disintegration agent, caused the tablets to break up rapidly.

Chemistry, Pharmaceutical↗
PubMed2005

Xanthan and galactomannan (from M. scabrella) matrix tablets for oral controlled delivery of theophylline.

Directly compressed theophylline tablets, containing commercial xanthan (X) (Keltrol) and a highly hydrophilic galactomannan (G) from the seeds of Mimosa scabrella (a brazilian leguminous tree called bracatinga) as release-controlling agents, were obtained. Gums were used at 4, 8, 12.5 and 25% (w/w), either alone or in mixture (X:G 1:1). During galactomannan extraction process, the biopolymer was dried in a scale up, by vacuum oven (VO) or spray dryer (SD). The in vitro drug release was evaluated at different time intervals during 8 h using apparatus 1 (USP 26) at 100 rpm. The pH of the dissolution medium (1.4) was changed to 4.0 and 6.8 after 2 and 3 h, respectively. Tablets containing G(SD) resulted in more uniform drug release than G(VO) ones, due to their smaller particle size. The drug release decreased with the increase of polymer concentration and all formulations at 25% w/w of gums showed excessive sustained release effect. The matrices made with alone X showed higher drug retention for all concentrations, compared with G matrices that released the drug too fast. The XG matrices were able to produce near zero-order drug release. The XG(SD) 8% tablets provided the required release rate (about 90% at the end of 8 h), with zero-order release kinetics. Tablets containing G(VO) in low concentration showed a complete erosion, while the others demonstrated fast hydration and swelling in contact with the dissolution medium. The release mechanism was a combination of diffusion and relaxation. The relative importance of these two processes varied with matrix composition. The XG(SD) 8% matrix showed higher contribution of polymer relaxation.

Administration, Oral↗
PubMed2006

Development and optimization of a novel sustained-release dextran tablet formulation for propranolol hydrochloride.

A novel oral controlled delivery system for propranolol hydrochloride (PPL) was developed and optimized. The in vitro dissolution profiles of sustained-release matrix tablets of racemic PPL were determined and compared with the United States Pharmacopeia (USP) tolerance specifications for Propranolol Hydrochloride Extended-Release Capsules. The influence of matrix forming agents (native dextran, hydroxypropyl methylcellulose (HPMC), cetyl alcohol) and binary mixtures of them on PPL release in vitro was investigated. A central composite design was applied to the optimization of a sustained-release tablet formulation. The sustained-release matrix tablets with good physical, mechanical and technological properties were obtained with a matrix excipient:PPL ratio of 60:40 (w/w), with a dextran:HPMC ratio of 4:1 (w/w) and with a cetyl alcohol amount of 15% (w/w). A comparative kinetic study of the present matrix tablets and commercial SUMIAL RETARD capsules (Spain) was established. The value for the similarity factor (f(2)=69.6) suggested that the dissolution profile of the present two sustained-release oral dosage forms are similar. Higuchi (diffusion) and Hixon-Crowell (erosion) kinetic profiles were achieved and this codependent mechanism of drug release was established.

Capsules↗
PubMed2006

Zero-order release of aspirin, theophylline and atenolol in water from novel methylcellulose glutarate matrix tablets.

A novel hydrocolloidal polymer, methylcellulose glutarate (MC-GA), was prepared by esterifying methylcellulose with glutaric anhydride. The formation of ester was confirmed by FTIR and NMR spectroscopy, DSC and elemental analysis. The physicochemical properties such as, rate of swelling in water, viscosity and hygroscopicity of MC-GA were determined and compared with those of methycellulose A (MC). Aspirin, theophylline and atenolol tablets were compacted on a Carver press using the wet granulation method. Each tablet contained: 200 mg active, 80 mg anhydrous lactose, 8 mg povidone, 4 mg magnesium stearate, 4 mg talc, 50mg MC or MC-GA (drug-to-polymer ratio, 4:1). Contrary to the first-order release profile of all the drugs from the MC matrix tablets, a zero-order release was obtained from the MC-GA matrix tablets in water.

Adrenergic beta-Antagonists↗
PubMed2006

Optimization of poorly compactable drug tablets manufactured by direct compression using the mixture experimental design.

The poor flowability and bad compressibility characteristics of paracetamol are well known. As a result, the production of paracetamol tablets is almost exclusively by wet granulation, a disadvantageous method when compared to direct compression. The development of a new tablet formulation is still based on a large number of experiments and often relies merely on the experience of the analyst. The purpose of this study was to apply experimental design methodology (DOE) to the development and optimization of tablet formulations containing high amounts of paracetamol (more than 70%) and manufactured by direct compression. Nineteen formulations, screened by DOE methodology, were produced with different proportions of Microcel 102, Kollydon VA 64, Flowlac, Kollydon CL 30, PEG 4000, Aerosil, and magnesium stearate. Tablet properties, except friability, were in accordance with the USP 28th ed. requirements. These results were used to generate plots for optimization, mainly for friability. The physical-chemical data found from the optimized formulation were very close to those from the regression analysis, demonstrating that the mixture project is a great tool for the research and development of new formulations.

Acetaminophen↗
PubMed2004

Modulating drug release with cyclodextrins in hydroxypropyl methylcellulose gels and tablets.

This paper reports on the effect of beta-cyclodextrin (beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on the diffusion and the release behavior of diclofenac sodium and sulphamethizole from HPMC K4M gels and matrix tablets. The gels were prepared with 0.5-2.0% polymer and different drug/CD mole ratios, and their viscosity, cloud point and drug diffusion coefficients were estimated. No differences in cloud point were observed. The viscosity of the gels strongly depended on HPMC proportions (from 0.7 to 100 mPa.s), which affected to a lesser extent the resistance to the diffusion of the drugs (D values from 60 x 10(-6) to 5 x 10(-6) cm(2)/s). The influence of CD on diffusion was particularly evident in gels prepared with polymer proportions above its entanglement concentration, 2.0% HPMC K4M. In these systems, while high drug/CD proportions enhanced the diffusivity preventing polymer/drug hydrophobic interactions, low drug/CD ratios hindered it. An excess of free CD, especially the bulky HP-beta-CD, made the diffusion of the complexes in the relatively low mesh size 2% polymer network more difficult. In the case of tablets, CD plays an additional role as dissolution rate promoter. To evaluate to what extent the balance between the increase in dissolution rate and the decrease in diffusion rate induced by CD determines drug release, matrix tablets were prepared by direct compression of 100 mg drug and 400 mg polymer/CD/lactose blends, whose composition was chosen following a simplex centroid design. A higher CD/lactose ratio significantly increased the release rate of hydrophobic drugs (sulphamethizole), but decreased the release rate of hydrophilic drugs (diclofenac sodium), indicating the predominance of a different contribution depending on the hydrophilicity of the drug. Therefore, the use of CD derivatives may be particularly useful to modulate drug release from HPMC gels and matrix tablets; the influence of these additives being dependent on the nature of the drug and on the molecular size and hydrophilic character of the CD used.

Cyclodextrins↗
PubMed2004

Studies on controlled release effervescent osmotic pump tablets from Traditional Chinese Medicine Compound Recipe.

A controlled release effervescent osmotic pump tablet (EOPT) of Traditional Chinese Medicine Compound Recipe (TCMCR), named Fuzilizhong prescription which includes acidic drugs consisted of many known and unknown effective components and has been used for several thousands years, was successfully prepared with sodium chloride, sodium hydrogen carbonate and hydroxypropylmethylcellulose(HPMC) as osmotic agents. Since the osmotic pressure in EOPT with sodium chloride and sodium hydrogen carbonate increased greatly, which was induced mostly by gas carbon dioxide generating from the reaction of sodium hydrogen carbonate and the acidic drugs in TCMCR after the fluid being imbibed into the compartment through the semipermeable membrane and the in vitro accumulative dissolution percent from prescription 3 was up to 96.6% at 14 hour, the problem that water insoluble drugs can not to be elementary osmotic pump tablet for its low dissolution rate was solved in the paper. On the basis of prescription 3, the drug in effervescent osmotic pump tablet was released controllably after HPMC was selected as retarder and has a good in-vitro-in-vivo correlation(IVIVC, r=0.9550). Threrfore, it could be concluded that the formulation of TCMCR is appropriate to being made into EOPT, which improves acidic drugs composed of soluble and poorly soluble components release more greatly and controllably. From the point of this, water insoluble drugs can be designed to elementary osmotic pump tablet for more complete dissolution release.

Algorithms↗
PubMed2004

Anomalous dissolution behaviour of tablets prepared from sugar glass-based solid dispersions.

In this study, anomalous dissolution behaviour of tablets consisting of sugar glass dispersions was investigated. The poorly aqueous soluble diazepam was used as a lipophilic model drug. The release of diazepam and sugar carrier was determined to study the mechanisms governing dissolution behaviour. The effect of carrier dissolution rate and drug load was tested with four different sugars, in the order of decreasing dissolution rates: sucrose, trehalose and two oligo-fructoses; inulinDP11 and inulinDP23 having a number average degree of polymerization (DP) of 11 and 23, respectively. Diazepam was incorporated in these sugar glasses in the amorphous state by means of freeze drying using water and tertiary butyl alcohol (TBA) as solvents. None of the tablets disintegrated during dissolution. Dissolution of 80% of the lipophilic drug within 20 min was found when diazepam and sugar dissolution profiles coincided. The sugar carrier and diazepam dissolved at the same rate, which was constant in time and fast. This condition was met for relatively slow dissolving carriers like the inulins or for low drug loads. For relatively fast dissolving carriers like sucrose or trehalose with high drug loads, release profiles of diazepam and sugar did not coincide: diazepam dissolved much more slowly than the sugars. In case of non-coinciding release profiles, diazepam release was split into three phases. During the first phase non-steady-state dissolution was observed: diazepam release accelerated and a drug rich layer consisting of crystalline diazepam was gradually formed. This first phase determined the further release of diazepam. During the second phase a steady-state release rate was reached: zero-order release was observed for both drug and carrier. During this phase, the remaining (non-crystallised) solid dispersion is dissolved without the further occurrence of crystallisation. The third phase, starting when all carrier is dissolved, involved the very slow dissolution of crystallised diazepam, which was present either as the skeleton of a tablet resulting in a zero-order release profile or as separate particles dispersed in the dissolution medium resulting in a first-order release. To understand the anomalous dissolution behaviour, a model is proposed. It describes the phenomena during dissolution of amorphous solid dispersion tablets and explains that fast dissolution is observed for low drug loads or slow dissolving carriers like inulin.

Diazepam↗
PubMed2005

Investigation of novel alginate-magnesium aluminum silicate microcomposite films for modified-release tablets.

Physicochemical properties of sodium alginate-magnesium aluminum silicate (SA-MAS) composite films were investigated and a potential as a film former of SA-MAS dispersion for modifying drug release from tablets was evaluated as well. Interaction between SA and MAS in the composite films was revealed using FTIR spectroscopy. Thermal behavior of the composite films was changed due to the complexation of SA and MAS. Powder X-ray diffractometry data suggested that a higher crystallinity of the composite film and a phase-separated microcomposite were formed. The composite films in the ratios of 1:0.5 and 1:1 showed the increases of tensile strength and percentage of elongation when compared with SA films. Water vapor permeability of the composite films tended to increase with increasing ratio of MAS. The decreases in water uptake and drug permeability in 0.1 M HCl were found in the composite films. A positive charge drug, propranolol HCl, provided a higher affinity on the composite films than a weakly acidic nonelectrolyte, acetaminophen, resulting in a longer lag time and a higher partition coefficient depending on the content of MAS in the composite films. This was due to the complex formation of propranolol HCl and MAS. Using SEM, the tablets coated with SA-MAS dispersion had a smooth surface, while those with SA dispersion showed a pinholing on the surface, resulting in a faster drug release. The drug release profiles of the tablets could be modified by coating with the composite film at different coating levels. This finding suggests that MAS could improve physicochemical properties of the SA films, leading to a novel coating material of the SA-MAS dispersion for modifying drug release from tablets.

Absorption↗
PubMed2006

Microenvironmental pH and microviscosity inside pH-controlled matrix tablets: an EPR imaging study.

Incorporation of pH modifiers is a commonly used strategy to enhance the dissolution rate of weakly basic drugs from sustained release solid dosage forms. Electron paramagnetic resonance imaging (EPRI) was applied to spatially monitor pH(M) and the rotational correlation time (tau(R)), a parameter which is closely related to the surrounding microviscosity inside HPMC (hydroxypropylmethylcellulose) matrix tablets. Fumaric, citric, and succinic acid were employed as pH modifiers. 4-(methylamino)-2-ethyl-5,5-dimethyl-4-pyridine-2-yl-2,5-dihydro-1H-imidazole-1-oxyl (MEP) was used as spin label. Fumaric and citric acid reduced the pH(M) to equal extents in the initial phase. With the progress of hydration, the more soluble citric acid diffused out from the tablet resulting in an increase in pH(M), originating at the outer layers. In contrast, fumaric acid maintained a constantly reduced pH(M) inside the entire tablet. Due to its lower acidic strength, succinic acid did not reduce the pH(M) as effectively as the other pH modifiers used. The more water-soluble acids stimulated the water penetration into the matrix system, thereby rapidly decreasing tau(R). Once the matrix tablets were hydrated, the included pH modifiers influenced tau(R) insignificantly. EPRI, a novel approach for monitoring pH(M) and tau(R) non-invasively and spatially resolved, was used successfully for the optimization of an pH-controlled formulation.

Chemistry, Pharmaceutical↗
PubMed2006

A study of tablet dissolution by magnetic resonance electric current density imaging.

The electric current density imaging technique (CDI) was used to monitor the dissolution of ion releasing tablets (made of various carboxylic acids and of sodium chloride) by following conductivity changes in an agar-agar gel surrounding the tablet. Conductivity changes in the sample were used to calculate spatial and temporal changes of ionic concentrations in the sample. The experimental data for ion migration were compared to a mathematical model based on a solution of the diffusion equation with moving boundary conditions for the tablet geometry. Diffusion constants for different acids were determined by fitting the model to the experimental data. The experiments with dissolving tablets were used to demonstrate the potential of the CDI technique for measurement of ion concentration in the vicinity of ion releasing samples.

Computer Simulation↗