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PubMed2000

Measurement of the adhesive force of fine particles on tablet surfaces and method of their removal.

The adhesion force of fine particles on the surface of tablets was measured by a centrifugal force and impact separation method. A Finededuster (FDD) was employed to remove fine particles from the tablet surface. The centrifugal force and impact separation method was suggested to be effective for measuring the adhesive forces between particles and the tablet surface, and effective disjoining force in the FDD could be estimated by comparison of the results obtained using these two methods. The FDD showed high removal efficiency regardless of how many tablets were processed at the same time. In either of these methods, critical particle size was about 10-20 microns, and larger particles were removed more efficiently. This critical particle size was similar to that observed for other mechanical properties of powders, such as angle of repose and flowability. We simulated particle residual percentage under various operation conditions by ANN (artificial neural network) analysis and multiple regression analysis. This simulation enabled us to predict how the efficiency of particle removal is affected by the interaction of the experimental and material factors.

Administration, Oral↗
PubMed2000

Response surface analysis applied to the preparation of tablets containing a high concentration of vegetable spray-dried extract.

This work relates to the formulation of tablets containing a high proportion of spray-dried extracts (SDEs) from Passiflora edulis leaves. The tablets were prepared by direct compression. Colloidal silicon dioxide was selected as a glidant and moisture adsorbent, cross-linked carboxymethycellulose was used as the disintegrant, microcrystalline cellulose was the filler/binder, and tricalcium phosphate as a spray-drying adjuvant. The colloidal silicon dioxide and cross-linked carboxymethycellulose quantities and their influences on the tablet hardness and disintegration time were studied by a central composite design. The model equations were fitted to the experimental data and then validated. It could be concluded that the colloidal silicon dioxide proportion increased the hardness, and the cross-linked carboxymethycellulose proportion determined a linear decrease of the disintegration time. The optimal values chosen were 2.0% Aerosil 200 and 2.5% Ac-Di-Sol. The tablets showed a hardness of 85.02 N and a disintegration time of 7.35 min.

Chemistry, Pharmaceutical↗
PubMed2000

Application of similarity factor in development of controlled-release diltiazem tablet.

Controlled-release grade hydroxypropylmethylcellulose (HPMC) or xanthan gum (XG) and microcrystalline cellulose (MCC) were employed to prepare controlled-release diltiazem hydrochloride tablets. The similarity factor f2 was used for dissolution profile comparison using Herbesser 90 SR as a reference product. Drug release could be sustained in a predictable manner by modifying the content of HPMC or XG. Moreover, the drug release profiles of tablets prepared using these matrix materials were not affected by pH and agitation rate. The f2 values showed that only one batch of tablets (of diltiazem HCl, HPMC or XG, and MCC in proportions of 3.0:3.0:4.0) was considered similar to that of the reference product, with values above 50. The unbiased similarity factor f2* values were not much different from the f2 values, ascribing to a small dissolution variance of the test and reference products. The amount of HPMC or XG incorporated to produce tablets with the desired dissolution profile could be determined from the curves of f2 versus polymer content. Hence, the f2 values can be applied as screening and optimization tools during development of controlled-release preparations.

Antihypertensive Agents↗
PubMed2000

Optimization and development of a core-in-cup tablet for modulated release of theophylline in simulated gastrointestinal fluids.

A triple-layer core-in-cup tablet that can release theophylline in simulated gastrointestinal (GI) fluids at three distinct rates has been developed. The first layer is an immediate-release layer; the second layer is a sustained-release layer; and the last layer is a boost layer, which was designed to coincide with a higher nocturnal dose of theophylline. The study consisted of two stages. The first stage optimized the sustained-release layer of the tablet to release theophylline over a period of 12 hr. Results from this stage indicated that 30% w/w acacia gum was the best polymer and concentration to use when compressed to a hardness of 50 N/m2. The second stage of the study involved the investigation of the final triple-layer core-in-cup tablet to release theophylline at three different rates in simulated GI fluids. The triple-layer modulated core-in-cup tablet successfully released drug in simulated fluids at an initial rate of 40 mg/min, followed by a rate of 0.4085 mg/min, in simulated gastric fluid TS, 0.1860 mg/min in simulated intestinal fluid TS, and finally by a boosted rate of 0.6952 mg/min.

Analysis of Variance↗
PubMed1999

Matrix tablets of carrageenans. II. Release behavior and effect of added cations.

Carrageenans are hydrocolloids in the rubbery state at standard conditions. They are useful excipients for controlled-release tablets. Three carrageenans, two kappa-carrageenans (Gelcarin GP-812 NF and GP-911 NF) and one iota-carrageenan (Gelcarin GP-379 NF), are analyzed regarding their release behavior in combination with sorption, swelling, and rheology. The iota-carrageenan has a higher substitution by sulfate groups. The kappa-carrageenan Gelcarin GP-812 NF contains a small amount of potassium chloride left over from processing. Water sorption of the pure materials was studied gravimetrically, and the rheology of different solutions (2% and 5% w/w) was studied by cup-cylinder rotation viscosimetry. Swelling was determined as the vertical expansion of the tablets with a specially designed swelling apparatus. Drug release from the tablets was performed by the USP paddle method for 8 hr. The data indicate that drug release increases when water sorption and swelling extent decrease and as viscosity increases. The order of release is nearly zero-order kinetics for theophylline monohydrate, a nonionic drug. Diffusion of the anionic drug diclofenac sodium is anomalous. In addition, the influence of the added salts potassium and calcium chloride on swelling and release was studied. Before tableting, physical mixtures of these salts with and without theophylline monohydrate were prepared. Swelling and release change in the same order, but this is only valid when the ionic interactions responsible for this are strong enough. Besides this, physical mixing of salts with the carrageenans can result in an increased release of drug caused by decreased cohesion of the matrix during drug release, mainly for calcium chloride.

Adsorption↗
PubMed1999

Use of tablet tensile strength adjusted for surface area and mean interparticulate distance to evaluate dominating bonding mechanisms.

In this study, tablet tensile strength has been adjusted for tablet surface area and the average distance between particles in compacts of different materials. The aim of the study was to evaluate the feasibility of using this concept to assess the dominating interparticulate bonding mechanisms. Adjustment of the tensile strength for both tablet surface area and mean pore radius gave similar bonding strength values for materials bonding mainly by weak distance forces (crystalline lactose, sucrose, and microcrystalline cellulose) almost independently of compaction pressure. However, particle size and other factors may still affect the compensated strength values. The bond strength was much higher and more varied for materials bonding also with solid bridges (potassium chloride, sodium chloride, and possibly also sodium bicarbonate and amorphous lactose). For these materials, particle size and compaction pressure had a substantial effect on the bond strength. It is probably the formation of continuous bridges between adjacent particles that is important in these materials rather than the surface properties and the average distance between particles positioned at some distance from each other. Hence, adjusting the tensile strength of compacts does not necessarily reflect all the dominating factors responsible for interparticulate bonding. Nonetheless, adjustment for tablet surface area and mean pore radius allowed discrimination between different dominating interparticulate bonding mechanisms in these compacted materials.

Chemistry, Pharmaceutical↗
PubMed1999

Pharmaceutical evaluation of multipurpose excipients for direct compressed tablet manufacture: comparisons of the capabilities of multipurpose excipients with those in general use.

Recently, a novel type of multipurpose excipient (MPE) with high binding characteristics and high fluidity has been developed. In this study, the capabilities of MPEs (Ludipress and Microcelac) were compared with those of excipients in general use. Also, the effects on powder and tableting characteristics of the physical properties and contents of active ingredients were examined in tablets prepared with these MPEs by the direct compression method. Multipurpose excipients mixed with adjuvants such as fillers, binders, lubricants, disintegrants, and the like show superior fluidity and compressibility. Tablets containing very small amounts of highly active ingredients with little dispersion were prepared. However, with increases in active ingredient content, each of the physical properties was affected strongly by the properties of the active ingredient. Tablets with appropriate hardness and disintegration characteristics could be prepared by mixing of different types of MPEs.

Chemistry, Pharmaceutical↗
PubMed1999

In vitro conditions for the study of the in vivo performance of sustained-release theophylline matrix tablets administered in fasted conditions and with a high-fat diet.

Dissolution profiles of theophylline (TP) from three types of sustained-release (SR) matrix tablets (plastic [PL], lipid [LP], and hydrophilic [HP]) in different dissolution media, with and without enzymes, were established. Also investigated was the influence of a treatment of the tablets with peanut oil prior to the dissolution test. The in vivo behavior of the tablets under the fasted state and with the concomitant administration with a high-fat diet was previously evaluated; the diet produced changes in the absorption profiles for the three matrix tablets in comparison with fasted administration. Level A correlations were obtained between cumulative percentage dissolved (CPD) and cumulative percentage absorbed (CPA). For the fasted condition, better correlations were obtained with water as the dissolution medium for the HP and LP matrix; for PL matrix, the best correlation was obtained with a medium with gradual change of pH. The pretreatment with peanut oil showed better correlations for the fed state.

Animals↗
PubMed2001

Design and evaluation of a two-layer floating tablet for gastric retention using cisapride as a model drug.

A new kind of two-layer floating tablet for gastric retention (TFTGR) with cisapride as a model drug was developed. The in vitro drug release was determined, and the resultant buoyancy and the time-buoyancy curve were plotted. Because of the sodium bicarbonate added to the floating layer, when immersed in simulated gastric fluid (SGF) the tablet expands and rises to the surface, where the drug is gradually released. The in vitro drug release of this kind of two-layer dosage was controlled by the amount of hydroxypropylmethylcellulose (HPMC) in the drug-loading layer. Generally, the more HPMC, the slower the drug releases. Because cisapride has greater solubility in SGF than simulated intestinal fluid (SIF), its in vitro drug dissolution in SGF is faster than in SIF. One of the distinguishing characteristics of this kind of tablet is the separate regulation of buoyancy and drug release. The idea developed in this experiment can be used as a general modelfor the design of other tablets for gastric retention.

Body Fluids↗
PubMed2002

Investigation of flow properties of powders by means of a uniaxial tester, in relation to direct tablet compression.

Unexpected poor flowability during commercial production of a direct compression tablet formulation initiated an investigation of the flow properties of the powder mixture and its components by means of a uniaxial tester. The failure function--a curve describing the strength of the powder bed as a junction of the maximum main stress that has consolidated the bed--of the powder mixture and its components was determined. The drug was more cohesive than the filler, which was somewhat more cohesive than the powder mixture. Three excipients--a hinder, a glidant and a lubricant constituting 3.5 w/w% of the formulation improved the flowability of the mixture of active ingredient and filler. The failure function discriminated powder mixtures with poor flow from mixtures with medium or good flow. However, it was not possible to discriminate medium from good flow by means of the failure function. Attempts to correlate univariately the flow property parameters of the powder mixtures with particle size data or flow property data of included active ingredient and filler batches failed. Therefore a multivariate approach was tested. Principal component analysis (PCA) and projection to latent structures by means of partial least squares (PLS) were employed. An excellent PCA model was obtained with the flow properties of the powder mixture. A good PCA model of tableting performance--based on tablet weight variation and tablet machine speed-was obtained.

Drug Compounding↗
PubMed2002

Hydrodynamic flows around tablets in different pharmacopeial dissolution tests.

We investigated the hydrodynamic flows around tablets during several pharmacopeial dissolution tests: the rotating basket (RB), paddle (PD), flow-through cell (FT), and disintegration (DI) tests. The determination of hydrodynamic flow was based on the dissolution rate of United States Pharmacopeial salicylic acid nondisintegrating calibrators, and showed that, compared with the PD and RB methods, the FT method produced a lower hydrodynamic flow value whereas the DI method produced a higher value. The hydrodynamic flows during the PD and RB tests appeared to be similar at the same rotational speed, although the flow patterns around the tablet differed; with the RB method, homogeneous dissolution occurred from all surfaces of the tablet, while with the PD method, dissolution from the lower surface was slower. The use of a sinker seemed to enhance dissolution from the lower surface. Such differences in hydrodynamic flow could explain the apparently different dissolution behaviors of disintegrating prednisone and nondisintegrating acetaminophen tablets when assessed by the PD and RB methods. These differences in hydrodynamic flow between in vitro tests should be considered when choosing dissolution tests for studying in vitro/in vivo relationships and for quality control purposes.

Anti-Infective Agents↗
PubMed2003

Evaluation of the effects of khaya gum on the mechanical and release properties of paracetamol tablets.

A study of the comparative effects of khaya gum and two standard binding agents-polyvinylpyrrolidone (PVP) and gelatin--on crushing strength and friability, and the disintegration and dissolution characteristics of paracetamol tablets was made. The crushing strength-friability ratio (CSFR), the disintegration times, D, and the dissolution times t50, t90, and t1 (derived from the equation of Noyes and Whitney), all increased with an increase in binder concentration; however, the dissolution rate constants, k1 and k2, decreased. The ranking for the values of CSFR for tablets containing the different binders was PVP > gelatin > khaya gum. The ranking for D and the dissolution times was gelatin > khaya gum > PVP, whereas the ranking for the dissolution rate constants was PVP > khaya gum > gelatin. There were significant linear correlations between CSFR, D, t50, t90, and t1 for the tablets. There were also significant correlations between k1 and D, t50, t90, and t1, and between k2 and t90. The results suggest that khaya gum could be useful as an alternative binding agent to produce tablets with particular mechanical strength and drug release profiles.

Acetaminophen↗
PubMed2004

Tableting of Eudragit RS and propranolol hydrochloride solid dispersion: effect of particle size, compaction force, and plasticizer addition on drug release.

The application of a solid dispersion (SD) system of propranolol HCl and Eudragit RS was evaluated in the preparation of prolonged release tablets. The effects of SD size fraction, compaction force, and inclusion of plasticizers [namely diethylphtalate (DEP) and triethylcitrate (TEC)] on crushing strengths of matrices and release profile of drug were also investigated. The results showed that when compressed as a tablet, the SD system was more efficient in prolonging drug release than physical mixture. This effect was due to formation of much harder tablets of the SD system (crushing strength 8.5 kg) compared with those of physical mixtures (crushing strength 2.7 kg). All matrices of the SD system showed release rate patterns that were best described by the Higuchi equation. It was also shown that the rate of drug release decreased from 19.8% to 9.13% min(-1/2) as the SD size fraction decreased from 300-350 to 125-250 microm. However, further reduction of size fraction did not significantly affect tablet crushing strength and drug release rate. Increase in compaction force from 5 to 30 kN increased the crushing strength of matrices from 2.9 to 13.6 kg. However, the rate of drug release remained nearly unchanged beyond compaction pressure of 10 kN, indicating that crushing strength of matrices in the range of 8.5-13.6 kg did not affect drug release rate. The addition of 5% or 10% of either plasticizer (DEP or TEC) led to an increase in crushing strength of matrices and more retardation of drug release. This effect was more pronounced for higher concentrations of plasticizers. This effect was probably due to more plastic deformation of matrices under the compaction force, which helped matrices to retain their shape throughout the dissolution test.

Antihypertensive Agents↗
PubMed2004

Mucoadhesive delivery systems. II. Formulation and in-vitro/in-vivo evaluation of buccal mucoadhesive tablets containing water-soluble drugs.

From the previous work (Part I), mucoadhesive formulae containing 5% CP/65% HPMC/30% lactose and 2% PC/68% HPMC/30% mannitol as well as formulae based on sodium carboxymethyl cellulose (SCMC) were selected. Medicated tablets were prepared using diltiazem hydrochloride (DZ) and metclopramide hydrochloride (MP) in two different doses (30 and 60 mg). The effect of drug and dose on the mucoadhesive properties and in-vitro drug release was evaluated. All formulae produced extended drug release (over 8 to 12 h). Polyacrylic acid based matrices (PAA) showed Fickian's diffusion release pattern for both drugs. SCMC ensured zero-order release for DZ, which deviated to anomalous behavior in case of MP. Doubling the dose significantly reduced the bioadhesion strength (p<0.05) with a slight improvement in drug release rate. The formulation of bilayer tablets containing drug-free layer and medicated layer enhanced the drug release without affecting the bioadhesive performance. The bilayer tablet formulated with 2% PC/68% HPMC/30% mannitol (PC2) was selected for studying the in-vivo metoclopramide release in four healthy volunteers. The tablet ensured controlled drug release for 12 h, in addition, good correlation (r=0.9398) was observed between in-vitro and in-vivo data. The effect of ageing on selected formulae containing DZ and MP, respectively, was studied. Storage at 40 degrees C and 75% relative humidity for 6 months didn't influence the mucoadhesive performance, however, an enhanced released rate was observed.

Adhesiveness↗
PubMed2004

Mucoadhesive delivery systems. I. Evaluation of mucoadhesive polymers for buccal tablet formulation.

Different types of mucoadhesive polymers, intended for buccal tablet formulation, were investigated for their comparative mucoadhesive force, swelling behavior, residence time and surface pH. The selected polymers were carbopols (CP934, and CP940), polycarbophil (PC), sodium carboxymethyl cellulose (SCMC) and pectin representing the anionic type, while chitosan (Ch) as cationic polymer and hydroxypropylmethyl cellulose (HPMC) as a non-ionic polymer. Results revealed that polyacrylic acid derivatives (PAA) showed the highest bioadhesion force, prolonged residence time and high surface acidity. SCMC and chitosan ensured promising bioadhesive characteristics, whilst HPMC and pectin exhibited weaker bioadhesion. Different polymer combinations as well as formulations were evaluated to improve the mucoadhesive performance of the tablets. Bioadhesive tablet formulations containing either 5% CP934, 65% HPMC and 30% spray-dried lactose or 2% PC, 68% HPMC and 30% mannitol showed optimum mucoadhesion and suitable residence time. SCMC, when formulated individually, exhibited promising bioadhesion, acceptable swelling, convenient residence time and surface pH. In-vivo trials of these formulations proved non-irritative and prolonged residence of the mucoadhesive tablets on human buccal mucosa for 8 to 13 h.

Adhesiveness↗
PubMed2004

Multivariate methods in the development of a new tablet formulation: optimization and validation.

In a previous study of the development of a tablet formulation approximately 100 excipients were characterized in screening experiments using multivariate design. Acceptable values for important responses were obtained with some of the formulations. The relationships between the properties of the excipients and the responses were evaluated using PLS. In this study additional experiments were performed in order to validate models obtained from the screening study and to find a formulation of suitable composition with desired tablet properties. A formulation with the desired disintegration time was found with the additional experiments and the agreement between observed and predicted values was fair for the tablets that did disintegrate. A limitation of this study was that tablets from four experiments did not disintegrate within the set time limit. The lack of agreement between observed and predicted values of these four experiments was probably due to the nature of one of the factors in the design. Considering the reduced experimental design the results are still encouraging.

Chemistry, Pharmaceutical↗
PubMed1999

The influence of engravings on the sticking of tablets. Investigations with an instrumented upper punch.

The purpose of this study was to investigate the influence of engravings on the sticking of tablets. Therefore, an instrumented upper punch capable of measuring the pull-off force, which occurs when the punch detaches itself from the upper surface of a tablet, was equipped with small cones of different angles between the punch face and the cones' lateral face. The cones could be screwed into a threaded hole at the center of the punch face. The adhesion forces of two formulations known to stick to engravings during production increased with a greater steepness of the cones' lateral face. With microencapsulated acetylsalicylic acid, no quantitative differences could be found between the adhesion forces obtained with plain and modified punch faces, indicating that the sticking behavior of the substance was not affected by shear forces. Starch 1500 showed higher adhesion force signals in comparison to those obtained with a plain punch face. Microcrystalline cellulose, which gave no adhesion force signals with a plain punch face and did not stick to the cones, showed distinct pull-off signals. The instrumented upper punch equipped with shear cones is a valuable instrument for detecting the adhesion caused by engravings and is therefore a helpful tool for tablet formulation development and the design optimization of tablet identification.

Adhesiveness↗
PubMed2003

Composite film-coated tablets intended for colon-specific delivery of 5-aminosalicylic acid: using deesterified pectin.

Combinations of Eudragit RS and deesterified pectin, polygalacturonic acid (PGA), or its potassium and sodium salts, when applied as a film coat, has a potential value as a colon-specific delivery system. Dispersions of PGA in Eudragit RS were used as the film former for coating of 5-aminosalicylic acid (5-ASA) tablet cores. Drug release behavior was assessed, in vitro, under simulating conditions in term of pH and time to in vivo during their transit to the colon. Negligible drug release occurred during first 5 hr where the coated tablets were in the stomach and small intestine. After that, the pectinolytic enzymes were added into the pH 6.8 medium to simulate the in vivo condition where there is the digestion of bacteria in the colon. The release of 5-ASA from the coated tablets occurred linearly as a function of time. Drug release depended on the composition of the mixed film, as well as the ratio of Eudragit RS to PGA or its salts. The highest drug release from the coated tablets of about 40% was obtained when the ratio of Eudragit RS to potassium salt of PGA was 2.5 to 1. Drug release profiles seemed to conform to the mechanism involving the osmotically driven release and formation of channels in the film caused by dissolution of PGA salts. Channel formation was, in most cases, activated by the presence of pectinolytic enzymes, showing that the PGA in the mixed film was subjected to enzymic breakdown. In conclusion, PGA could be used as an additive in Eudragit RS films to control the release of colonic delivery system.

Acrylic Resins↗