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At least 739 records · Page 41Linked to original sources

PubMed2005

Tablet computers in the veterinary curriculum.

Tablet computers offer a new method of information management in veterinary medical education. With the tablet computer, students can annotate class notes using electronic ink, search for keywords, and convert handwriting to text as needed. Additional electronic learning resources, such as medical dictionaries and electronic textbooks, can be readily available. Eleven first-year veterinary students purchased tablet computers and participated in an investigation of their working methods and perceptions of the tablet computer as an educational tool. Most students found the technology useful. The small size and portability of the tablet allowed easy transport and use in a variety of environments. Most students adapted to electronic notetaking by the second week of classes; negative experiences with the tablet centered on a failure to become comfortable with taking notes and navigating on the computer as opposed to writing and searching on paper. A few performance-related problems, including short battery life, were reported. Tablet software allowed conversion of faculty course notes from a variety of original formats, meaning that instructors could maintain their original methods of note preparation. Adopting a consistent naming convention for files helped students to locate the files on their computers, and smaller file sizes helped with computer performance. Collaboration between students was fostered by tablet use, which offers possibilities for future development of collaborative learning environments.

Attitude to Computers↗

PubMed1999

Study of accelerated storage conditions affecting physical characteristics, in-vitro dissolution and stability of bioadhesive containing tablets

The effect of storage at different temperatures and relative humidities on directly compressed tablets of indometacin containing 20% polycarbophil was studied for up to 16 weeks. The prepared tablets were stored in closed containers of type III glass under different conditions of temperature (30 degrees C, 40 degrees C and 50 degrees C), in open petri dishes at room temperature, at relative humidity (RH) (31%, 79.3% and 98%), and combinations of temperature and relative humidity (30 degrees C/92.9% RH, 40 degrees C/79.5% RH and 50 degrees C/65% RH). The tablet properties such as mean weight, hardness, disintegration, in-vitro dissolution and drug content were monitored just after preparation and after 2, 4, 8, 12 and 16 weeks of storage. The tablets mean weight was significantly (p < 0.05) increased at RH 98% and at 30 degrees C/92.9% RH and non-significantly increased at 79.3% RH, 40 degrees C/79.5% RH and 50 degrees C/65% RH. There was no effect of temperature on mean weight. The hardness of the tablets increased slightly at 31% RH and decreased at 79.3% RH and at 40 degrees C/79.5% RH and became zero at 98% RH and at 30 degrees C/92.9% RH. The increase in temperature caused slight increase in tablets hardness. Tablets stored at 98% RH and at 30 degrees C/92% RH showed an increase in disintegration time associated with a decrease in rate of dissolution and indometacin content. No effect on drug content or dissolution profile was observed as a result of storage under other conditions. These findings point out to the importance of proper protection of indometacin tablets containing polycarbophil from high temperature and humidity conditions in order to ensure stability of the drug.

Journal Article↗

PubMed2000

Studies on vaginal bioadhesive tablets of acyclovir.

Bioadhesive vaginal tablets were prepared using poly(acrylic acid) (PAA); Methylcellulose (MC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC) and hydroxypropylmethyl cellulose (HPMC) as bioadhesive polymers in different concentrations and acyclovir as drug by direct compression technique (DCT) and wet granulation technique (WGT). Physical tests were applied to the tablets. The swelling behavior of vaginal tablets in distilled water, lactic solution and cow vagina, acyclovir release rate in lactic solution and bioadhesion to vaginal mucosa in cow vagina, in situ, were investigated. Swelling of the tablets containing HPC, CMC and MC was very rapid and caused disintegration of the tablets. The swelling behaviour of the tablets containing HPMC lasted 6 h in lactic solution. The force (N) necessary to detach the tablets from the vaginal tissue was found to depend on concentration and type of the bioadhesive polymer. The tablets containing HPMC needed the most detachment force.

Acyclovir↗

PubMed2002

Mass variation tests for coating tablets and hard capsules: rational application of mass variation tests.

The mass variation test is a simplified alternative test version of the content uniformity test. In the case of coating tablets and capsules, the mass variation test is principally applied to test the inner cores or fillings containing the active ingredient. However, some exceptions exist in pharmacopoeias. The effects of tablet coating and capsule shell on the results of the mass variation test were studied. The mass variation of outer crusts (coatings, capsule shells) and inner cores (core tablets, fillings) was measured separately in several products. The effects of coating on weight variability were very large for sugar-coated tablets. Relative standard deviation (RSD) of the formulation weight (RSD(W)) of sugar-coated tablets (2.73%) was larger than that of plain tablets (0.77%). The cause of the large RSD(W) is the large variation the weight of sugar-coating accounting for 44% of formulation weight. In the case of film-coated tablets, the effect of coating weight on the mass variation test was very small because the rate of coating in comparison to the whole weight was small. In the case of hard capsules, the usage of whole formulation weight resulted in underestimation of variations of filling weight. The differences between dosage forms in the applicability of the mass variation test are caused by differing weight proportions and variability of the outer coatings or shells. To avoid the underestimation of mass variation for hard capsules, a corrected acceptance value is useful. For all the dosage units, the mass variation test can principally be applied to determine which mass is expected to be proportional to the content of the active ingredient. However, some modification of acceptance values enables application of the mass variation tests to inapplicable cases, such as when the RSD of drug concentration (RSD(C)) is larger than 2%.

Algorithms↗

PubMedDate not supplied

Evaluation of two new megestrol acetate tablet formulations in humans.

The bioequivalence of two new investigational 160 mg tablets, one containing the regular form and the other a micronized form of megestrol acetate, was determined relative to a commercially available 40 mg tablet (Megace). The tablets were administered to 24 male subjects in a three-way cross-over study, balanced for sequence, with a week between administrations. The 40 mg tablets were administered q.i.d. at 08.00, 12.00, 18.00 and 22.00 h, while the 160 mg tablets were administered once at 08.00 h. Plasma samples were collected at appropriate times out to 96 h after administration and were analysed for megestrol acetate with a validated high performance liquid chromatographic procedure. Based on the times to maximum plasma concentrations (2.5 to 2.8 h), the absorption rate constant was the same for each of the tablets. Relative to the 40 mg q.i.d. dose, the 160 mg regular and the 160 mg micronized tablets had mean relative bioavailabilities of 97 per cent and 118 per cent, respectively.

Adult↗

PubMed2002

Development and in vivo evaluation of buccal tablets prepared using danazol-sulfobutylether 7 beta-cyclodextrin (SBE 7) complexes.

The aim of the present work was to develop a mucoadhesive controlled-release formulation of danazol-sulfobutylether 7 beta-cyclodextrin (SBE 7) complex and to evaluate the feasibility of improving the bioavailability of danazol via the buccal route. Different types of polymers, polycarbophil (PC) and hydroxypropylmethyl cellulose (HPMC) were mixed with danazol-SBE 7 complex and compressed into tablets. These tablets were evaluated for their dissolution and mucoadhesion properties and for drug absorption in female beagle dogs. Increased mucoadhesion was observed for PC-containing tablets compared with HPMC tablets. As the concentration of polymer increased, drug release decreased, and PC-containing tablets gave slower release compared to HPMC tablets. In vivo bioavailability performed in dogs showed that the perorally administered danazol-SBE 7 complex and the danazol-SBE 7 (in PC matrix) buccal tablets had absolute bioavailabilities of 64% and 25%, respectively, that are significantly greater than 1.8% observed for the commercial formulation Danocrine. The increased bioavailability was attributed to the enhanced solubility consequent to complexation, and the possible avoidance of first-pass metabolism upon buccal administration.

Administration, Buccal↗

PubMed2001

Controlled and complete release of a model poorly water-soluble drug, prednisolone, from hydroxypropyl methylcellulose matrix tablets using (SBE)(7m)-beta-cyclodextrin as a solubilizing agent.

Sustained-release formulations such as hydroxypropyl methylcellulose (HPMC)-based hydrophilic matrix tablets of poorly water-soluble drugs often result in incomplete release because of the poor solubility and dissolution rate of the drug in the hydrophilic matrix. Sulfobutylether-beta-cyclodextrins ((SBE)(7M)-beta-CDs) have been known to improve the solubility of such drugs by forming inclusion complexes. The present paper deals with the modification of drug release from an HPMC-based matrix tablet of a sparingly water-soluble drug, prednisolone (PDL), using (SBE)(7M)-beta-CD as a solubilizing agent. Tablets were prepared by direct compression of a physically mixed PDL, (SBE)(7M)-beta-CD, and polymer. On exposure to water, an in situ PDL:(SBE)(7M)-beta-CD complex was formed in the gel layer, and enhanced drug release relative to a control formulation was observed (lactose used as the excipient instead of (SBE)(7M)-beta-CD ). Other possible changes due to the incorporation of (SBE)(7M)-beta-CD in the formulation were also probed. Incorporation of (SBE)(7M)-beta-CD lead to a higher water uptake relative to the control (lactose) formulation. For a fixed total tablet weight, polymer type, and loading, the drug release rate appeared to depend on the molar ratio of (SBE)(7M)-beta-CD to PDL and not the absolute amount of (SBE)(7M)-beta-CD present in the matrix tablet. This work shows that incorporation of (SBE)(7M)-beta-CD into the matrix tablets could be considered in designing a sustained-release tablet of poorly water-soluble drugs.

Cyclodextrins↗

PubMed2004

Adhesive tablet effective for treating canker sores in humans.

A new mucoadhesive tablet, which releases natural active agents for pain reduction and rapid healing of canker sores, has been prepared and characterized. Adhesive tablets were prepared by compression molding of mixed powders of crosslinked polyacrylic acid and hydroxypropyl cellulose, absorbed with citrus oil and magnesium salt. The rate of tablet erosion and the rates of citrus oil and magnesium release were determined as well as the adhesiveness of the tablet using bovine gingival tissue and an Instron tensiometer. A clinical trial was conducted on 248 volunteers who had canker sores. Tablets adhere well to the mucosal tissue and gradually erode for 8 h releasing the citrus oil in a zero-order pattern whereas the magnesium is released during a period of 2 h. Both experimental and plain tablets were effective in reducing pain and decreasing healing time (p < 0.05) without adverse side effects. However, the tablets loaded with active agents were more effective.

Adhesives↗

PubMed2005

Tuning the polymer release from hydrophilic matrix tablets by mixing short and long matrix polymers.

In this work a rotating disc method was developed for studying the dissolution process of "bimodal" polymer tablets, whose dissolution rates have been tuned by mixing low-molecular weight and high-molecular weight samples of poly(ethylene oxide) in various proportions. The tablets were prepared along different routes, by mixing the polymer fractions as powders or by mixing on a molecular level so that the effect of tablet heterogeneity could be assessed, but also by purifying the original powders so the effect of additives could be determined. When the mixed tablet was dominated by the low-molecular weight fraction, a faster dissolution was observed for the tablet mixed at the powder level. In those cases small gel pieces were released from the tablet during the whole dissolution process. As long as no gel piece erosion was observed, it did not matter if the two polymer fractions were blended on the molecular level or on the powder level, the steady-state dissolution rate was the same. The presence of small amounts of additives in the nonpurified commercial samples had no significant effect on the tablet dissolution within the uncertainty of the experiment.

Calorimetry, Differential Scanning↗

PubMed2006

Prediction of tablet hardness based on near infrared spectra of raw mixed powders by chemometrics.

The purpose of this research is to elucidate the effect of lubricant mixing on tablet hardness by near-infrared (NIR) chemometrics as a basic study of process analytical technology. Formulation cellulose (F-C) consisted of sulpyrine (SP), microcrystalline cellulose (MC), and magnesium stearate (MgSt). Formulation lactose/starch (F-L) consisted of SP bulk drug powder, spray-dried lactose (SL), corn starch (CS), and MgSt. First, F-L and F-C without MgSt were mixed in a twin-shell mixer for 60 min. MgSt was added to the mixed powder, and was mixed for various mixing times, after which the mixed powders were compressed by 8-mm diameter punch and die. NIR spectra of raw mixed powders of F-L and F-C were taken using a reflection type of Fourier transform NIR spectra spectrometer, and chemometric analysis was performed using principal component regression (PCR). The tablet hardnesses of F-L and F-C decreased with increasing mixing time. All NIR spectra of the mixed powders of F-L and F-C fluctuated depending on mixing time. In order to predict tablet hardness before tablet compression, NIR spectra of F-L and F-C mixed powders were analyzed and evaluated for hardness by PCR. The minimum standard error of cross-validation values could be realized by using five- and six-principal component models, respectively. In the cases of F-L and F-C, the relationships between the actual and predicted tablet hardnesses showed straight lines, respectively. In the regression vectors of F-L and FC, the peaks related to hydrogen groups of SP, CS, and MC appeared as positive peaks. In contrast, the peaks related to hydrocarbon due to MgSt appeared as negative peaks in the regression vectors. The calibration models to evaluate the tablet hardness were obtained based on NIR spectra of raw mixed powders by PCR. This approach to predicting tablet hardness prior to compression could be used as a routine test to indicate the quality of the final product without spending time and energy to produce samples of questionable quality.

Cellulose↗

PubMed2006

Reduced tabletability of roller compacted granules as a result of granule size enlargement.

The mechanism for the frequently observed "loss of reworkability or tabletability" of dry-granulated (DG) powders was investigated in detail using microcrystalline cellulose (MCC). It was hypothesized that granule size enlargement is the primary mechanism to the phenomenon. Detrimental effects of size enlargement on tabletability of plastic materials are predictable based on the physical model of interparticulate bonding within a tablet. In absence of extensive fracture of particles/granules, larger particles/granules exhibit lower surface area available for bonding thus lower tensile strength when compressed under identical conditions. Size effects were first demonstrated using different grades of MCC powders, both whole and sieved, of different particle size distributions. Regardless grade and sieve fraction, larger particles always resulted in lower tabletability, that is, lower tensile strength at the same compaction pressure. It was subsequently shown that enlargement of granules also reduced powder tabletability regardless grade of MCC. Tabletability of sieved granules after roller compacted for one, two, and four times decreased monotonically with increasing granule size but independent of the total number of roller compaction. Moreover, tabletability of fine granules (44-106 microm) was higher than that of coarse MCC powder (Avicel PH-200). These results suggest that the primary mechanism for reduced tabletabilty of DG granules of MCC is granule size enlargement rather than "work-hardening."

Cellulose↗

PubMed1975

Water-sorption properties of tablet disintegrants.

The water-sorption properties of four tablet disintegrants, starch, sodium carboxymethylcellulose, sodium starch glycolate, and a cation-exchange resin, were examined in the form of powders and in compressed tablets prepared from calcium phosphate dibasic dihydrate. Dissolution properties of the tablets compare well to the water-sorption properties. The effect of storage in the presence of water vapor upon tablets containing the various disintegrants was evaluated in terms of tablet hardness and disintegration time. Differences in the effects produced in the various tablet formulations can be related to the differing mechanisms whereby the disintegrants effect tablet rupture. Photomicrographic data support the conclusions drawn from the water-sorption, disintegration, and dissolution studies. Sodium starch glycolate and the cation-exchange resin merit careful consideration by formulators using calcium phosphate dibasic dihydrate or similar direct compression matrixes.

Absorption↗

PubMed1977

Determination of porosity and pore-size distribution of aspirin tablets relevant to drug stability.

Total porosity and pore-size distribution of aspirin tablets prepared from aspirin, starch USP, and precipitated colloidal silicon dioxide were determined using mercury porosimetry. The model represented a hydrolyzable drug substance in combination with simple excipients. The role of starch and silicon dioxide on the microstructure of the tablets was investigated, as was the chemical stability of various systems. In general, the porosity of tablets containing a constant quantity of starch increased linearly with silicon dioxide concentration. Examination of the pore-size distribution, however, revealed that a low concentrations silicon dioxide functioned primarily to reduce the size and volume of coarse pores representing the spaces between the agglomerates of starch and aspirin particles. This effect was optimum at 3%. A further increase in silicon dioxide concentration produced tablets with relatively larger pore sizes. Studies of changes in the porosity characteristics of tablets as influenced by water vapor over time showed distinct differences in this complex parameter. A unique trend in the change of the pore-size distribution was noted with tablets containing 3% silicon dioxide. These observations are discussed relative to the stability of aspirin tablets in which this concentration of silicon dioxide produced a maximum stabilizing effect.

Aspirin↗

PubMed1979

Dissolution systems for chloramphenicol tablet bioavailability.

The relationship between chloramphenicol (I) tablet bioavailability and in vitro dissolution rates was examined. The effect of solid food on the I tablet and powder bioavailability was also studied. Five tablets of I were selected for bioavailability testing on the basis of the dissolution rates of 18 I tablets (250 mg) determined by several methods. Compound I, 500 mg, was administered orally to five subjects, following overnight fasting, according to a crossover design. The bioavailability parameters were obtained from urinary I excretion. Among the five formulations studied, only one tablet (F) showed significantly poorer bioavailability. The dissolution rates at pH 1.2 did not give the same rank order as the bioavailability. The dissolution rate of Tablet F showed remarkable pH dependency. The dissolution rates at pH 4 showed good correlation with in vivo bioavailability data. The bioavailability of I powder was not affected by solid food. Tablet F, which had poor bioavailability in the fasting state, showed good bioavailability when administered just after the standard breakfast.

Adult↗

PubMed1981

Reversed-phase high-performance liquid chromatographic analysis of liothyronine sodium and levothyroxine sodium in tablet formulations: preliminary studies on dissolution and content uniformity.

Levothyroxine sodium was estimated from tablet formulations of levothyroxine sodium and liotrix (liothyronine sodium-levothyroxine sodium combination tablet). The procedures consisted of the addition of 3,3-,5-triiodothyronine as the internal standard to the pulverized sample, followed by an acidic butanol extraction, evaporation, and injection onto a muBondapak reversed-phase high-performance liquid chromatographic column. The eluent was methanol-water-phosphoric acid (50:50:0.1), and the effluent was monitored by UV detection at 254 nm. A standard linear calibration curve was obtained for direct standard solutions equivalent to 18-225 micrograms of levothyroxine sodium/tablet. The procedure is sensitive enough for single-tablet analysis. Using this procedure, content uniformity studies were performed on liothyronine sodium tablets, levothyroxine sodium tablets, and liotrix tablets. The procedure also was adapted for conducting dissolution studies on levothyroxine sodium tablets in deionized water using the rotating-paddle method.

Chromatography, High Pressure Liquid↗

PubMed1982

Effect of moisture and crushing strength on tablet friability and in vitro dissolution.

The friability and dissolution of a formulation of compressed tablets were studied by varying the granulation moisture and tablet crushing strength. A general quadratic response surface model was used to analyze the data. The response surface contour plots of tablet friability consisted of a series of ellipsoidal curves. The optimum friability corresponding to a granulation moisture content and a tablet crushing strength was a simple minimum. The in vitro dissolution contour plots showed a stationary ridge system. Along the ridge, a large number of combinations of tablet crushing strength and granulation moisture represented 100% drug dissolution. The contour overlays of friability and dissolution contour plots showed a region where both the friability and dissolution requirement could be met. The analysis of the data by means of multiple linear regression was helpful in understanding the role of granulation moisture and tablet crushing strength on tablet friability and in vitro dissolution.

Hardness↗

PubMed1983

External scintigraphy in monitoring the behavior of pharmaceutical formulations in vivo I: technique for acquiring high-resolution images of tablets.

A new method for monitoring tablet disintegration in vivo was developed. In this method, the tablets were labeled with a short-lived radionuclide, technetium 99m, and monitored by a gamma camera. Several innovations were introduced with this method. First, computer reconstruction algorithms were used to enhance the scintigraphic images of the disintegrating tablet in vivo. Second, the use of a four-pinhole collimator to acquire multiple views of the tablet resulted in high count rates and reduced acquisition times of the scintigraphic images. Third, the magnification of the scintigraphic images achieved by pinhole collimation led to significant improvement in resolution. Fourth, the radioinuclide was incorporated into the granulation so that the whole mass of the tablet was uniformly labeled with high levels of activity. This technique allowed the continuous monitoring of the disintegration process of tablets in vivo in experimental animals. Multiple pinhole collimation and the labeling process permitted the acquisition of quality scintigraphic images of the labeled tablet every 30 sec. The resolution of the method was tested in vitro and in vivo.

Computers↗

PubMed1984

Generic tolbutamide tablet dissolution: intralot and interlot variation.

Dissolution profiles for 62 lots of tolbutamide tablets from six manufacturers have been characterized using the USP paddle-stirrer apparatus. Results of paddle-stirrer dissolution for percent drug dissolved at 10, 20, and 30 min correlated well (r2 = 0.7444) with results from the USP rotating-basket test for 39 lots of tolbutamide. Interlot and intralot variability in tolbutamide dissolution was highly dependent on the manufacturer. For one product, the intralot range (for six paddle-stirred tablets) of percent drug dissolved after 30 min was 50-68% while the maximum interlot range for mean dissolution was 58-104%. One lot failed to meet both the rotating-basket and the paddle-stirrer dissolution specifications. Tablet response to aging at 60, 75, and 98% relative humidity over time was also highly manufacturer specific. The innovator's product repeatedly dissolved well when fresh or aged at all humidities. Dissolution from some generic tablets was dramatically depressed by humidity aging, even after only 3 d. Pretreatment of tablets with simulated gastric fluid modified the dissolution profile of one poorly dissolving lot of tablets. Results indicate that manufacturing quality control is highly variable among tolbutamide tablets.

Humidity↗