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PubMed1985

Influence of the granulation technique and starting material properties on the lubricating effect of granular magnesium stearate.

Magnesium stearate has been granulated in four ways to produce lubricant granulations with different properties. The lubricating properties, as well as the tablet properties with the granulated lubricant, were evaluated on tablets prepared from a mixture of dicalcium phosphate, corn starch and microcrystalline cellulose. The lubricating effect of the magnesium stearate granulations showed a similar pattern regardless of the granulation technique used except for a granulation with providone. Increasing the particle size of the magnesium stearate granulation increased the amount of lubricant required to obtain lubrication similar to powdered magnesium stearate. Variations in the specific surface area of the starting materials could be masked by using them in granular form.

Chemistry, Pharmaceutical↗
PubMed2002

Loss of regulation of lipogenesis in the Zucker diabetic rat. II. Changes in stearate and oleate synthesis.

De novo lipogenesis and dietary fat uptake are two major sources of fatty acid deposits in fat of obese animals. To determine the relative contribution of fatty acids from these two sources in obesity, we have determined the distribution of c16 and c18 fatty acids of triglycerides in plasma, liver, and epididymal fat pad of Zucker diabetic fatty (ZDF) rats and their lean littermates (ZL) under two isocaloric dietary fat conditions. Lipogenesis was also determined using the deuterated water method. Conversion of palmitate to stearate and stearate to oleate was calculated from the deuterium incorporation by use of the tracer dilution principle. In the ZL rat, lipogenesis was suppressed from 70 to 24%, conversion of palmitate to stearate from 86 to 78%, and conversion of stearate to oleate from 56 to 7% in response to an increase in the dietary fat-to-carbohydrate ratio. The results suggest that suppression of fatty acid synthase and stearoyl-CoA desaturase activities is a normal adaptive mechanism to a high-fat diet. In contrast, de novo lipogenesis, chain elongation, and desaturation were not suppressed by dietary fat in the ZDF rat. The lack of ability to adapt to a high-fat diet resulted in a higher plasma triglyceride concentration and excessive fat accumulation from both diet and de novo synthesis in the ZDF rat.

Adipose Tissue↗
PubMed1984

Relative bioavailability of enteric coated pellets, stearate and ethylsuccinate formulations of erythromycin.

In a randomized three-phase crossover study, 12 healthy male volunteers were given three 12-hourly 500-mg doses of erythromycin base, as enteric coated pellets in capsules (2 X 250 mg), erythromycin stearate tablet (1 X 500 mg), or erythromycin ethylsuccinate sachet (1 X 500 mg). The reaction time after administration of the pellets is significantly longer than after the stearate or ethylsuccinate formulations. The peak serum concentrations are higher for the pellets after both the 1st and 3rd dose. The time to reach peak concentrations is significantly longer for the pellets than for the stearate and ethylsuccinate formulations. The area under the serum concentration/time curve during 0-8 h after both doses is highest for the pellets. In conclusion, these findings indicate that despite the longer lag (1.8-1.2 h), the extent of gastrointestinal absorption and bioavailability of erythromycin is apparently greater for the base pellets than for the stearate and ethylsuccinate formulations.

Adult↗
PubMedDate not supplied

Preparation of polymeric microspheres by the solvent evaporation method using sucrose stearate as a droplet stabilizer.

Polymeric microspheres containing nicardipine hydrochloride (HCl) as a reference drug were prepared with the acrylic polymers Eudragit RS and L by the solvent evaporation method. Different concentrations of sucrose stearate as a droplet stabilizer were used. Sucrose stearate affected the diffusion rate of the solvent from the preliminary emulsion droplets to the outer phase for the formation of microspheres. Increasing concentrations of sucrose stearate in the formulations caused increasing porosity on the surface of the microspheres. However, a correlation between the concentrations of sucrose stearate and diameters of microspheres could not be assessed. From this point of view, during processing, applied stirring rate was important.

Drug Compounding↗
PubMed2001

[The firmness of Avicel PH 102 and Avicel PH 301 compression and the effect of magnesium stearate] ].

The paper evaluated the strength of compacts made of microcrystalline cellulose of two types used as dry binders in the technology of direct compression of tablets, i.e. Avicel PH 102 and Avicel PH 301. The effect of three concentrations of the lubricant magnesium stearate (0.4; 0.8; 1.2%) on the strength of tablets made from these substances was also evaluated. Tables were compressed using three forces of compression (3; 3.5, and 4 kN). On the basis of the obtained results it can be concluded that Avicel PH 102 provides, under identical forces of compression, stronger compacts than Avicel PH 301 does. It has been further found that a magnesium stearate concentration of 0.4 markedly decreases the tensile strength of Avicel PH 102 tablets, and another marked decrease is observed with a concentration of 1.2%. The decrease in the tensile strength of Avicel PH 301 compacts due to magnesium stearate is not so marked as in Avicel PH 102 tablets, and with stearate concentrations of 0.4% and 1.2% the difference in strength is not of such importance in comparison with the previous concentrations.

Cellulose↗
PubMed1981

Influence of two haloalkanes on the redox behavior of hepatic microsomal cytochrome b-5 and its possible relationship to stearate desaturase.

The possible interaction of two haloalkanes - bromotrichloromethane and 1,2-dibromo-1,2-dichlorethane - with stearate desaturase was assessed in hepatic microsomes from rats fed a high carbohydrate diet which elevates the levels of stearate desaturase. Both compounds shifted the redox steady state of NADPH reduced hepatic microsomal cytochrome b-5 towards ferricytochrome b-5 and enhanced the re-oxidation of NADH reduced hepatic microsomal cytochrome b-5. The equilibrium constants for the enhancement of microsomal electron transfer by the haloalkanes in these preparations were 2.2 +/- 0.3 mM and 0.46 +/- 0.1 mM for bromotrichloromethane and 1,2-dibromo-1,2-dichlorethane, respectively. The haloalkane mediated enhancement of the oxidation of cytochrome b-5 in hepatic microsomes from rats fed a high carbohydrate diet was diminished by KCN and the inhibitors of cytochrome P-450, CO and/or metyrapone, as well as by fasting of the experimental animals. The I50 values for KCN inhibition of the effects of the haloalkanes on the re-oxidation of cytochrome b-5 (01 mM) were identical to the I50 for KCN inhibition of stearate desaturase (Oshino et al., 1966). The haloalkanes did not affect the activity of hepatic microsomal NADH- or NADPH-cytochrome c reductase, the autoxidation of purified trypsin-cleaved ferrocytochrome b-5 or the conversion of stearoyl CoA to oleate. It is concluded that bromotrichloromethane and 1,2-dibromo-1,2-dichloroethane stimulate hepatic microsomal electron transfer from NADH via cytochrome b-5 by interacting with cytochrome P-450 and with stearate desaturase.

Animals↗
PubMed1994

Posttranslational acylation of the transferrin receptor in LSTRA cells with myristate, palmitate and stearate: evidence for distinct acyltransferases.

When incubated with [3H]myristate or [3H]palmitate, LSTRA cells, a murine T cell line, incorporated radiolabel into a protein of 95 kDa as analyzed by SDS-polyacrylamide gel electrophoresis. This dually acylated protein was identified as the transferrin receptor by immunoprecipitation with a monoclonal anti-transferrin receptor antibody. Acylation of the transferrin receptor was posttranslational and occurred via ester or thioester linkages. Analysis of radiolabeled transferrin receptor protein from [3H]myristate-labeled cells by acid hydrolysis followed by thin layer chromatography revealed the exclusive presence of [3H]myristate. Labeled transferrin receptor protein from [3H]palmitate-labeled cells contained predominantly [3H]stearate and smaller amounts of [3H]palmitate. This is in contrast to the protein-tyrosine kinase p56lck, which in [3H]palmitate-treated LSTRA cells, incorporated primarily [3H]palmitate. An analog of myristic acid, 5-nonanyloxyfuran-2-carboxylic acid, inhibited the incorporation of [3H]myristate, but not [3H]palmitate or [3H]stearate into transferrin receptor protein, suggesting that these acylation events are distinct. These studies indicate that the murine transferrin receptor is acylated posttranslationally with myristate, palmitate and stearate and suggest that more than one acyltransferase activity is responsible for its acylation.

Acylation↗
PubMed1976

Effect of dietary palmitate, stearate, oleate and linoleate on the tissue lipid and systolic blood pressure of the rat.

The nutritional effects of palmitate, stearate, oleate and linoleate were correlated with the percentage of each fatty acid in the dietary lipid but were found to be largely independent of the total amount of fat in the diet. Increasing the proportion of linoleate in diet fat to levels as high as 52% of the fat, increased theproportion of fat observed in the carcass. Increased linoleate and/or oleate resulted in increased concentrations of cholesterol in body fat deposits. The maximum weight of the perirenal fat pads occurred when diet fat contained about 43% oleate and 19% stearate. Increasing the stearate decreased the cholesterol concentration in plasma. The systolic blood pressure was decreased slightly when the amount of diet fat was increased.

Adipose Tissue↗
PubMed1992

[The effect of two lubricants (magnesium stearate and pruv) in the formation of tablets of four anti-ulcer agents/ by means of direct compression].

In this research we study the influence of two lubricants-Magnesium Stearate and Pruv--on the tablets elaboration of Cimetidine, Ranitidine, Famotidine and Pirenzepine by direct compression. The presence of 0.5% of lubricants improved the flow of all the formulations, but especially the Famotidine's formulation. The formulations with Magnesium Stearate had the worst results in tests of friability and tensile strength. All tablets with drugs and Pruv had high data in indentation hardness. The tablets of Cimetidine, Famotidine and Pirenzepine with Magnesium Stearate had less time of disintegration.

Anti-Ulcer Agents↗
PubMed1998

Studies on neurosteroids. VII. Determination of pregnenolone and its 3-stearate in rat brains using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

An assay method for pregnenolone and its 3-stearate in rat brains has been developed using LC-atmospheric pressure chemical ionization (APCI) isotope dilution MS. The extraction of the rat brain homogenate containing deuterated internal standards (ISs) with organic solvent followed by silica gel mini-column chromatography gave two fractions containing pregnenolone and its 3-stearate together with the respective IS. Each fraction was derivatized into 3-acetate-20-methyloxime and 20-methyloxime, respectively, followed by silica gel mini-column chromatography to remove the excess reagents, and then each derivatized fraction was applied onto reversed-phase LC-APCI-MS. The method was applied to the determination of these steroids in the gray matter and olfactory bulbs of rat brains, which were divided into control and acute stressed specimens. Although pregnenolone in both regions of the rat brains increased more than five times after stress, its 3-stearate decreased after stress.

Animals↗
PubMedDate not supplied

Time-dependent inhibition of theophylline elimination by erythromycin stearate.

The effect of erythromycin stearate at a dose of 1 g daily on theophylline disposition was studied in six healthy adult males. The mean value of 5.46 h for the theophylline half-life after 48 h pretreatment with erythromycin stearate was not significantly different from the control value of 5.24 h. The half-life value of 8.48 h after a 1-week course of the antibiotic, however, represented a significant increase (p less than 0.005). Theophylline disposition 1 week after the last dose of the antibiotic was not significantly different from the control. It is suggested that therapeutic doses of erythromycin stearate for a week or more could impair the disposition of concurrently administered theophylline. The impairment however, is reversible, being absent a week after the last antibiotic dose.

Adult↗
PubMed1981

Interaction of tablet disintegrants and magnesium stearate during mixing I: Effect on tablet disintegration.

The effect of magnesium stearate on the disintegration of tablets was studied. Three different preblends, containing a slightly or a strongly swelling disintegrant, were mixed before compression with magnesium stearate for different time periods. The results show that a strongly swelling disintegrant, such as sodium starch glycolate in contrast to potato starch, can reduce the deteriorating effect of hydrophobic lubricants on tablet disintegration. However, the interaction between magnesium stearate and potato starch or sodium starch glycolate and the resulting differences in disintegration characteristics can be masked by the use of disks in the USP disintegration apparatus.

Aspirin↗
PubMed1988

Chemical, physical, and lubricant properties of magnesium stearate.

Three batches of commercial magnesium stearate were characterized in terms of their fatty acid composition, moisture content, and specific surface area. None of these variables appeared to have any effect on the lubricant activity of the samples. The lubricant properties of the compound were further examined using three hydrates of laboratory-prepared (pure) magnesium stearate. Based on the results obtained from the pure samples, it appears that differences in the lubricant properties of magnesium stearate are correlated with differences in moisture content and crystalline structure.

Chemical Phenomena↗
PubMed1997

Preparation and Organized Assembly of Nanoparticulate TiO2-Stearate Alternating Langmuir-Blodgett Films

Nanoparticulate TiO2-stearate Langmuir-Blodgett-type monolayers and multilayers were directly obtained by using TiO2 hydrosol as the subphase. The surface pressure-versus-surface area isotherms showed that the monolayer could be compressed to a mean molecular area of 0.25 nm2. The monolayer was transferred onto a CaF2 or Si substrate at a dipping speed of 18 cm/min and surface pressure of 25 mN/m. It exhibited Y-type multilayer films over the range investigated (1-30 layers) with a transfer ratio of 1.0 ± 0.1. FTIR transmission spectra and linear infrared dichroic spectra provided evidence of the formation of a stable organic/inorganic alternating multilayer with nanoparticulate TiO2 between the organic monolayers. There is only slight absorption in the range of the C;equals;O stretching vibration band of the carboxylic group with the 3- and 6-nm TiO2 nanoparticles. This means that TiO2 particles are packed closely; i.e., the surface coverage is very high. A possible structure consists of layers of nanoparticles in close-packed form with two stearate ion layers inbetween. But it can be seen that there are some carboxylic groups (1700 cm-1) not connected to the 20-nm TiO2 nanoparticle. Electron microscopic (TEM) images of TiO2-stearate monolayers show that high-coverage monolayers were obtained when the surface pressure increased to 25 mN/m and the dipping speed to 18 cm/min. Copyright 1997Academic Press

Journal Article↗
PubMedDate not supplied

Absorption of erythromycin stearate and enteric-coated erythromycin base after a single oral dose immediately before breakfast.

To study the absorption of different preparations of erythromycin in the fasting state, 500 mg stearate (tablets) and 500 mg base (enteric-coated pellets) were given immediately before a standardised breakfast to 24 young, healthy volunteers in an open, random, cross-over trial. The serum peak concentration appeared earlier and was higher after intake of the stearate tablets than after intake of the base pellets; however, there was no difference in the area under the serum concentration vs. time curves (AUC) between the two preparations. The bioavailability of erythromycin stearate in tablet form and of erythromycin base in the form of enteric-coated pellets thus appears comparable when taken on an empty stomach.

Absorption↗
PubMed1991

Palmitate and stearate kinetics in the rat during sepsis and trauma.

Kinetics of plasma free palmitate and stearate were measured in control and septic-traumatized rats to determine the contribution plasma free fatty acids make to increased resting energy expenditure. Measurements were made at 24 hr after insult using a primed, 4-hr continuous infusion of selected (1-14C) fatty acid. The plasma concentration of palmitate was increased and stearate was decreased in sepsis-trauma rats compared to plasma concentrations in healthy control rats. Fatty acid turnover rates during sepsis-trauma were changed from control turnover rates in the same direction as plasma concentrations. Oxidation rates for palmitate and stearate at 24 hr after induction of sepsis-trauma were not different from oxidation rates in control rats. Plasma free fatty acids were concluded not to exhibit increased oxidation after sepsis-trauma and not to contribute extra energy during hypercatabolism. This finding contrasts with glucose and amino acids which have an increased oxidation rate during hypercatabolism.

Animals↗
PubMed2003

Structural properties of magnesium stearate pseudopolymorphs: effect of temperature.

A thorough review of the relevant literature reveals that the interaction between water vapour and magnesium stearate, in contrast to many other metal soaps, is not properly understood. The structural modifications associated with the up-take or loss of water of vegetable-derived commercial magnesium stearate powders exposed to humid air or vacuum at room temperature are investigated using standard powder X-ray diffractometry. It is found that in such conditions magnesium stearate reacts reversibly with the vapour phase with structural consequences very similar to the high temperature transition between the crystalline and rotator phases of other anhydrous metal soaps. When temperature is increased under dry nitrogen the diffraction band characteristic of the rotator phase shifts towards higher angle values and the corresponding lattice spacing increases at the rate of 6.9x10(-4)C(-1). Melting takes place gradually above 100 degrees C as revealed by the collapse of the diffraction band and the growth of the broader diffusion band characteristic of the liquid state. Full clarification of the structure of the hydrated and dried phases proves impossible based on powder diffraction spectra obtained with conventional high resolution X-ray diffraction equipment.

Chemical Phenomena↗
PubMed1995

Dental anxiety and the absorption of orally administered erythromycin stearate.

Erythromycin stearate is an acid labile antibiotic, therefore fear and apprehension, which are known to affect gastric motility, may produce erratic absorption resulting in lower serum levels. The mean (SD) serum erythromycin concentration 75 minutes after a 1.5 gm oral dose of erythromycin stearate to 45 patients was 8.7 (4.8) mg/L and ranged widely from 0.4 to 20.5 mg/L. The serum concentration of erythromycin was below therapeutic levels (1.0 mg/L) in two patients. No significant association was found between anxiety and serum levels of erythromycin when age, gender, and gastric distress were taken into account. It is concluded that dental anxiety may indirectly influence the uptake of oral erythromycin stearate; but this relationship is complex, and there is no evidence from this study that increased dental anxiety decreases the uptake of the drug.

Adult↗