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PubMedDate not supplied

Formulation and in vitro characterization of ciprofloxacin floating and bioadhesive extended-release tablets.

Ciprofloxacin is mainly absorbed in the proximal areas of the gastrointestinal tract. The purpose of our study was production of floating-bioadhesive tablets to lengthen the stay of drug in its absorption area. Effervescent tablets were made using sodium carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose (HPMC), polyacrylic acid (AA), polymetacrylic acid (MAA), citric acid, and sodium bicarbonate. Tablets with 5% effervescent base had longer lag time than 10%. The type of polymer had no significant effect on the floating lag time. All tablets floated atop the medium for 23-24 hr. Increasing CMC caused higher mucoadhesion than AA (p < 0.05). All formulations showed a Higuchi, non-Fickian release mechanism. Tablets with 10% effervescent base, 80% CMC/20% HPMC, or 80% AA /20% MAA seemed desirable.

Acrylic Resins↗
PubMed2006

Evaluation of disintegrating time of rapidly disintegrating tablets by a paddle method.

A paddle method for measurement of the disintegrating time of orally disintegrating tablets with rizatriptan benzoate as a model drug was evaluated. The paddle method employed a dissolution test assembly with tablets immersed in disintegrating medium through a fastened sinker. Paddle stirring rate, opening of the sinker sieve, and tablet crushing strength influenced disintegrating time greatly. A logarithmic relationship was observed between disintegrating time and paddle revolution speed, while disintegrating time values and tablet crushing strength were fitted to a linear equation. The paddle method values with limited deviation were in good correlation with in vivo results. The paddle method was employed to optimize the disintegrating time of rizatriptan benzoate orally disintegrating tablets using a factorial design. The best-fit quadratic equation with a regression coefficient of 0.996 was highly predictive, which was indicative that the paddle method was precise and applicable in formulation optimization.

Chemistry, Pharmaceutical↗
PubMed2001

Oral sustained-release bioadhesive tablet formulation of didanosine.

The objective of this study was to formulate a hydrogel-forming bioadhesive drug delivery system for oral administration of didanosine (ddI). The aim of this tablet dosage form is to improve the oral absorption of ddI by delivering it in small doses over an extended period and localizing it in the intestine by bioadhesion. Compressed tablets of ddI using Polyox WSRN-303, Carbopol 974P-NF, and Methocel K4M as the bioadhesive release rate-controlling polymers were prepared. The effect of polymer concentration on the release profile and in vitro bioadhesion of the matrix tablets was studied. Tablet formulations with Polyox WSRN-303 (10%) and Methocel K4M (30%) showed 93 and 90% drug release, respectively, after 12 h. The drug release was found to be linear when fitted in the Higuchi equation (square-root time equation), suggesting zero-order release. Carbopol 974-P-NF was found to inhibit the complete release of ddI because of drug-polymer interaction; hence, is not suitable for formulation of ddI. Drug diffusion and swelling of the polymer (anomalous Fickian release) was found dominant in ddI release. In general, in vitro bioadhesion increased with an increase in polymer concentration. Tablets containing a single polymer can be designed to form hydrogels serving the dual purpose of bioadhesion and sustained release.

Adhesives↗
PubMed2000

Influence of pharmacotechnical design on the interaction and availability of norfloxacin in directly compressed tablets with certain antacids.

Norfloxacin is a fluorquinolone that can interfere with antacids that contain aluminum and magnesium salts by complexation and modification of its solubility, which reduces its absorption and may lead to therapeutic failures. The purpose of this work was to evaluate the effect of the pharmaceutical design on this interaction and to develop a formulation of norfloxacin tablets in which this process could be avoided. Norfloxacin tablets were designed in 28 formulations. The interaction was studied in terms of in vitro dissolution behavior (USP 23, apparatus 2) in simulated gastric fluid with different doses of four commercially available antacid preparations. It was observed that dissolution rates were markedly reduced in the presence of all antacids studied. This phenomenon was practically avoided with some formulations of norfloxacin tablets in which a disintegrant (sodium starch glycolate or crospovidone) was included. These results indicated that the chelation among metal ions and norfloxacin could be affected by the delivering ability of the drug in the tablet. It was demonstrated that the pharmacotechnical design could modify an interaction process. Some formulations of tablets, in which the reduced dissolution rates in the presence of nonsystemic antacids in vitro was practically avoided, were developed by direct compression.

Antacids↗
PubMed2000

Multivariate methods in developing an evolutionary strategy for tablet formulation.

The aim of this study was to develop a new strategy for choosing excipients in tablet formulation. Multivariate techniques such as principal component analysis (PCA) and experimental design were combined in a multivariate design for screening experiments. Of a total 87 investigated excipients, the initial screening experiments contained 5 lubricants, 9 binders, and 5 disintegrants, and 35 experiments were carried out. Considering a reduced factorial design was used, the resulting PCA and partial least squares (PLS) models offered good insight into the possibilities of tablet formulation. It also offered solutions to the problems and clearly gave directions for optimum formulations. Further, it offered several alternatives for achieving quality formulations. Additional experiments conducted to validate and verify the usefulness of the model were successful, resulting in several tablets of good quality. The conclusion is that a multivariate strategy in tablet of formulation is efficient and can be used to reduce the number of experiments drastically. Combining multivariate characterization, physicochemical properties, experimental design, multivariate design, and PLS would lead to an evolutionary strategy for tablet formulation. Since it includes a learning strategy that continuously incorporates data for new compounds and from conducted experiments, this would be an even more powerful tool than expert systems.

Chemistry, Pharmaceutical↗
PubMed2000

Polymers with pH-dependent solubility: possibility of use in the formulation of gastroresistant and controlled-release matrix tablets.

Polymers usually utilized for gastroresistant film coating of tablets or pellets such as cellulose acetate phthalate (CAP), cellulose acetate trimellitate (CAT), hydroxypropylmethylcellulose phthalate (HPMCP), and Eudragit L and S were used in the preparation of drug/polymer matrix tablets. These tablets were prepared either by direct compression of both powders or by the formulation of microspheres that were then compressed. The microspheres were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffractometry analyses. Dissolution studies were finally carried out to verify if the tablets possessed gastroresistant or controlled-release characteristics. Except for Eudragit L, the polymers can be used under certain conditions in the formulation of modified-release tablets.

Acetaminophen↗
PubMed2000

Properties of hot-melt extruded theophylline tablets containing poly(vinyl acetate).

The objectives of this study were to investigate the properties of poly(vinyl acetate) (PVAc) as a retardant polymer and to study the drug release mechanism of theophylline from matrix tablets prepared by hot-melt extrusion. A physical mixture of drug, polymer, and drug release modifiers was fed into the equipment and heated inside the barrel of the extruder. The cylindrical extrudates were either cut into tablets or ground into granules and compressed with other excipients into tablets. Due to the low glass transition temperature of the PVAc, the melt extrusion process was conducted at approximately 70 degrees C. Theophylline was used as the model drug in this study. Theophylline was present in the extrudate in its crystalline form and was released from the tablets by diffusion. The Higuchi diffusion model and percolation theories were applied to the dissolution data to explain the drug release properties of the matrix systems. The release rate was shown to be dependent on the granule size, drug particle size, and drug loading in the tablets. Water-soluble polymers were demonstrated to be efficient release rate modifiers for this system.

Bronchodilator Agents↗
PubMed1999

Evaluation of the in vitro and in vivo performance of two sustained-release lithium carbonate matrix tablets. Effect of different diets on the bioavailability.

Two sustained-release (SR) lithium carbonate (Li) matrix tablets, which use a hydrophilic (HP) matrix of hydroxypropylmethylcellulose (Methocel 4K MP) and a lipid (L) matrix of hydrogenated castor oil (Cutina HR) as sustaining agents, have been studied. In vitro performance through dissolution tests in different media was established. The L and HP formulations were affected by the composition of the dissolution media, and liberation was complete in 8 hr using a variable-pH medium that simulates the gastrointestinal (Gl) pH. Liberation was better described by the diffusional model of the square root of time for the L matrix and by zero-order kinetics for the HP matrix. Absolute bioavailability (BA) and food-induced changes on BA of both formulations were studied. The in vivo study design was a 4 x 4 Latin square involving 12 subjects who received two tablets of a 300-mg dose of SR formulations while fasting or with a standardized normal, high-fat, or high-fat/high-protein meal. The results for both formulations showed no differences in the disposition parameters and mean residence time when the tablets were administered with any type of diet. Changes in rate of absorption were found when both types of tablets were administered with any class of diet. The analysis of the ratio Cmax/AUC (area under the curve) evidenced that changes in Cmax were attributable to a higher rate of absorption for the HP matrix and to a higher amount absorbed for the L matrix. In the last, high-fat and high-fat/high-protein diets produced higher AUCs than under fasting condition. The SR Li tablets formulated with hydrogenated castor oil were affected more by high-fat food, probably because of the increase of pancreatic and biliary secretions promoted by the meal, which would affect the matrix itself. The HP matrix was also affected, but to a lesser extent. The magnitude of the change in Cmax observed with this matrix probably is not important from a clinical point of view. Absolute BA was very low for the lipid matrix; in addition, since it is more seriously affected by food, probably it is not a good choice for a drug such as lithium. The in vivo behavior of the HP matrix makes it advisable to invest in efforts to achieve increased BA. Comparing in vitro and in vivo results, the focus should be achieving sustained, but complete, in vitro liberation in not more than 3 hr, with simulation of the transit time through the stomach and small bowel since lithium ion is only absorbed to this point.

Analysis of Variance↗
PubMed1999

Investigation of prandial effects on hydrophilic matrix tablets.

The prolonged release of drug from hydrophilic matrix tablets can be greatly affected by administration in connection with the intake of food. Changes of the tablet erosion are one of the main components of this effect. The aim of the present study was to identify the postprandial factors responsible for changes in tablet erosion and to develop predictive in vitro tests. Two formulations, one sensitive and the other robust to prandial effects in vivo, were investigated in vitro (a) in a complex physiological media simulating fasting and fed conditions; (b) according to a factorial experimental design that included agitation and pH concentrations of salt, surface-active agent, and nonionic solute as factors; and (c) at varying agitation intensities in three different sets of dissolution apparatus. Of the studied factors, only increased agitation enhanced the erosion of tablets in accordance with the in vivo effects of a meal. The other factors retarded erosion or had only minor effects. The hydrodynamic mechanical stress was thus considered to be the main factor responsible for postprandial effects on tablet erosion. The influence of changes in agitation and the opportunity to discriminate between sensitive and robust formulations differed among the three sets of dissolution apparatus. The modified USP II apparatus, operated at speeds of 50 and 100 rpm, is proposed as a discriminatory test.

Chemistry, Pharmaceutical↗
PubMed1999

Optimization of a tablet containing chlorthalidone.

In pharmaceutical technological research, optimization studies generally deal with the search for the formulation that is as effective and as functional as possible. The effect of a formulation parameter (the amount of lactose in the composition of the tablets) and of a technological parameter (compression pressure) on four physical characteristics (tablet thickness, friability, hardness, and drug dissolution rate) of tablets containing the antihypertensive drug chlorthalidone were studied. The results obtained indicate that, in the development of a tablet formulation, it is possible to identify the most suitable formulation by applying a simple optimization method. The effect of the microclimatic stress (temperature and humidity) was also evaluated, and it was found that the optimized tablets were no longer within limits that had been established for them. This may indicate that it is opportune to keep the storage conditions of the excipients under control before their use.

Algorithms↗
PubMed2003

Preparation and in vitro/in vivo evaluation of the buccal bioadhesive properties of slow-release tablets containing miconazole nitrate.

Slow-release buccal bioadhesive tablets of miconazole nitrate were prepared by using polymer mixtures of buccoadhesive materials such as hydroxypropylmethylcellulose, sodium carboxymethylcellulose, carbopol 934p, and sodium alginate. The physicochemical properties, swelling index, microenvironment pH, in vitro drug release, in vivo buccoadhesion time, and miconazole salivary concentrations of the prepared tablets were shown to be dependent on the type and composition of the buccoadhesive materials used. The dissolution of miconazole from all the prepared tablets into phosphate buffer (pH 6.8) was controlled and followed non-Fickian release mechanisms. All the prepared tablets gave reasonable buccoadhesion time (2.45-3.65 hr). Infrared spectroscopy and differential scan calorimetry studies revealed the absence of significant interactions between miconazole nitrate and the selected buccoadhesive materials. Duration of the antifungal activity as measured by the inhibition zone of Candida albicans by extracted human saliva was significantly longer (p < 0.05), compared with commercial miconazole oral gel (Daktaren oral gel). Based on the results obtained, the prepared slow-release buccoadhesive tablets of miconazole would markedly prolong the duration of the antifungal activity with more patient convenience.

Acrylates↗
PubMed2003

Evaluation of monolithic osmotic tablet system for nifedipine delivery in vitro and in vivo.

The aim of this study was to evaluate the monolithic osmotic tablet system (MOTS) containing a solid dispersion with the practically water-insoluble drug nifedipine in vitro and in vivo. In the drug release study in vitro, the release profiles of this system had almost zero-order kinetics. The influences of tablet formulation variables, sizes of the delivery orifice, membrane variables, and values of pH in the dissolution medium on nifedipine release from MOTS have been investigated. The results provided evidence that the tablet core played an important role in MOTS. While orifice sizes and membrane variables affected the nifedipine release rate, MOTS was independent of the dissolution medium. The appropriate orifice size was found to be in the range of 0.5-1.0 mm. The coating membrane incorporating hydrophilic polyethylene glycol (PEG) formed a porous structure. The human pharmacokinetics and relative bioavailability of MOTS containing nifedipine were compared with a commercial Adalat osmotic tablet system containing an equivalent dose of nifedipine following an oral single dose of 30 mg given to each of 11 healthy volunteers in an open, randomized crossover study in vivo. The relative bioavailability for MOTS was 112%. There was no statistically significant difference in the pharmacokinetic parameters between two dosage forms. It is concluded that the monolithic osmotic tablet controlled release system is feasible for a long-acting preparation as a once-daily treatment.

Adult↗
PubMed2004

Comparison studies on the percolation thresholds of binary mixture tablets containing excipients of plastic/brittle and plastic/plastic deformation properties.

Percolation theory has been used with great interest in understanding the design and characterization of dosage forms. In this study, work has been carried out to investigate the behavior of binary mixture tablets containing excipients of similar and different deformation properties. The binary mixture tablets were prepared by direct compression using lactose, polyvinyl chloride (PVC), Eudragit RS 100, and microcrystalline cellulose (MCC). The application of percolation theory on the relationships between compactibility, Pmax, or compression susceptibility (compressibility), gamma, and mixture compositions reveals the presence of percolation thresholds even for mixtures of similar deformation properties. The results showed that all mixture compositions exhibited at least one discreet change in the slope, which was referred to as the percolation threshold. The PVC/Eudragit RS100 mixture compositions showed significant percolation threshold at 80% (w/w) PVC loading. Two percolation thresholds were observed from a series of binary mixtures containing similar plastic deformation materials (PVC/MCC). The percolation thresholds were determined at 20% (w/w) and 80% (w/w) PVC loading. These are areas where one of the components percolates throughout the system and the properties of the tablets are expected to experience a sudden change. Experimental results, however, showed that total disruption of the tablet physical properties at the specified percolation thresholds can be observed for PVC/lactose mixtures at 20-30% (w/w) loading while only minor changes in the tablets' strength for PVC/MCC or PVC/Eudragit RS 100 mixtures were observed.

Acrylic Resins↗
PubMed2001

Time dependence of elastic recovery for characterization of tableting materials.

The purpose of this study was to complete information on elastic recovery during a compression cycle by measuring the expansion of the tablet after ejection, and thus, to measure the whole recovery process, which means the time dependency of elastic recovery. Two methods were applied: manual measurement by a micrometer screw, and a continuous measurement by thermomechanical analysis, always at a constant temperature and humidity. Elastic recovery of the tablet continued after ejection from the die, and the amount of expansion was different for the tableting materials used. The results showed that expansion continued for most of the materials over several days, until a steady state of the tablet and its physical properties was reached. The extent and the profiles of the elastic recovery curves were different for the tableting materials dicalcium phosphate dihydrate, carrageenan, microcrystalline cellulose, cellulose acetate, hydroxypropyl methylcellulose and theophylline monohydrate. There were slight differences between both the methods used. The profiles of the materials could be related to some properties of the materials.

Calcium Phosphates↗
PubMed2000

Tablet and capsule hydrophilic matrices based on heterodisperse polysaccharides having porosity-independent in vitro release profiles.

The purpose of the study was to investigate the release-controlling action of a swellable hydrophilic material based on heterodisperse polysaccharides (HP) in relation to the initial pore structure of the formulations. HP-based granules were produced under carefully controlled conditions and compacted into matrix tablets having equivalent tablet thickness. Quantification of pore structure using mercury porosimetry showed that the tablets had substantially different pore volumes and pore size distributions. Dissolution studies demonstrated that release of a water-soluble model compound, benzamide, from swollen matrices was affected neither by total porosity nor median pore diameter of the initial dry matrix. To extend the concept of porosity-independent release further, HP-based formulations containing either diclofenac sodium or propranolol HCl were contained within hard gelatin capsules in the form of uncompacted granules. This produced a dosage form with a high intraparticulate porosity in the dry state. Equivalent weights of the same formulations were also compacted into tablets. The in vitro release profiles from matrix tablets compacted from any of the formulations did not differ significantly from release profiles obtained when the same materials were contained uncompacted in hard gelatin capsules.

Benzamides↗
PubMed2000

Mercury porosimetry of mannitol tablets: effect of scanning speed and moisture.

Purpose of the work was to study the effect of the scanning speed of mercury porosimetry and moisture content of the sample on the mercury porosimetry result for mannitol tablets. Tablets were compressed at three different compression pressures from nonhygroscopic mannitol powder and granules. Pore structure of tablets was determined with three different scanning speeds of a high-pressure mercury porosimeter after storage in three different moisture conditions. With low scanning speed, smallest pores of tablets were determined more accurately. Small amounts of moisture, even as low as 1%, before evacuation in nonhygroscopic mannitol tablets decrease the porosity. Decrease in porosity was observed at a pore diameter range of 50-1000 nm, not at the smallest determined pores. Thus, the role of water in pharmaceutical samples appears to be complicated. Reasonably slow scanning is recommended in high-pressure mercury porosimetry. If total pore volume is the only parameter of interest, fast scanning can be used. Pretreatment of the samples by proper drying before mercury porosimetry is important.

Humidity↗
PubMed2003

A novel amylose corn-starch dispersion as an aqueous film coating for tablets.

A novel aqueous coating dispersion of amylose-rich corn starch (Hylon VII) was evaluated in an aqueous film-coating process of tablets using an instrumented laboratory-scale pan-coating apparatus. The influence of two independent process variables, the coating temperature and the atomizing air pressure, on the properties of the coated tablets were investigated. The preuse stability of aqueous coating dispersion (i.e., amylose corn-starch precipitate) was studied using a powder X-ray diffraction (XRD) technique. The crystallinity of amylose starch in the coating dispersion was found to increase slightly during 9 months of storage (in a refrigerator 6 +/- 2 degrees C). The film coatings of an aqueous amylose-rich starch dispersion were successfully applied onto tablets without any significant drawbacks, such as nozzle blockage or related problems. It was found that the temperature in the coating pan had a significant influence on the film surface roughness, mechanical strength, and drug release in vitro. When the lowest coating temperature (30 degrees C) was used, rougher film coatings were obtained due to overwetting. At higher temperatures (up to 50-60 degrees C), lower surface roughness and higher mechanical strength values for the coated tablets were obtained. With the present amylose starch dispersion, the atomizing air pressure had a minor influence on the quality of the coating. Under appropriate coating conditions, a smooth tablet film coating was produced with this new, natural, and inexpensive amylose starch dispersion.

Amylose↗
PubMed2003

Influence of the aqueous film coating process on the properties and stability of tablets containing a moisture-labile drug.

The effects of an aqueous film coating process on the morphology and storage stability of hydroxypropyl methylcellulose-coated tablets containing a moisture-labile model drug (acetylsalicylic acid, ASA) were evaluated using an instrumented side-vented tablet pan coater. Coating parameters studied were inlet air absolute humidity 5 g/m3 and 12 g/m3, spraying air pressure 100 kPa and 500 kPa, pan air temperature 35 degrees C and 55 degrees C, and coating solution flow rate 2.2 g/min and 7.8 g/min. The surface roughness of the coatings was measured with a laser profilometer and the chemical hydrolysis of the model drug ASA with an UV-spectrophotometer. The film-coated tablets were stored at 25 degrees C/60% RH and 40 degrees C/75% RH for three months. The high absolute humidity of the inlet air increased the residual water content and surface roughness of the coated tablets. Using a lower coating solution flow rate, higher spraying air pressure and pan temperature the coatings were smooth and homogeneous. In both ambient and accelerated storage conditions, the roughness of the coatings and the hydrolysis of ASA increased, but this was independent of the film coating process. Uniform and smooth hydroxypropyl methylcellulose coatings can be achieved by improved control of process parameters related to the application of the coating solution and water evaporation of the tablet surface.

Air Movements↗