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PubMed1986

Drug-excipient interactions resulting from powder mixing. IV: Role of lubricants and their effect on in vitro dissolution.

Two lubricants, magnesium stearate and sodium stearyl fumarate, were compared under identical mixing conditions to study their roles in drug-excipient interactions. After prolonged mixing, sodium stearyl fumarate did not interact with the drug or excipients; as a result, the disintegration time and drug dissolution rate from hand-filled, uncompacted capsules were not adversely affected. In contrast, magnesium stearate did exhibit drug-excipient interactions which resulted in lamination and subsequent adhesion of the lubricant to the drug-crospovidone agglomerates. These interactions adversely affected the disintegration time and drug dissolution rate from hand-filled, uncompacted capsules. Although the initial specific surface area of magnesium stearate was higher than that of sodium stearyl fumarate, flaking of magnesium stearate due to particulate-particulate interactions caused a large increase in the surface area. The adhesion of the magnesium stearate flakes to the drug-crospovidone agglomerates resulted in a decrease in the drug dissolution rate.

Chemistry, Pharmaceutical↗
PubMed2002

Molecular species of PC and PE formed during castor oil biosynthesis.

As part of a program to elucidate castor oil biosynthesis, we have identified 36 molecular species of PC and 35 molecular species of PE isolated from castor microsomes after incubations with [14C]-labeled FA. The six [14C]FA studied were ricinoleate, stearate, oleate, linoleate, linolenate, and palmitate, which were the only FA identified in castor microsomal incubations. The incorporation of each of the six FA into PC was better than that into PE. The [14C]FA were incorporated almost exclusively into the sn-2 position of both PC and PE. The incorporation of [14C]stearate and [14C]palmitate into 2-acyl-PC was slower compared to the other four [14C]FA. The incorporation does not show any selectivity for the various lysoPC molecular species. The level of incorporation of [14C]FA in PC was in the order of: oleate > linolenate > palmitate > linoleate > stearate > ricinoleate, and in PE: linoleate > linolenate > oleate > palmitate > stearate > ricinoleate. In general, at the sn-1 position of both PC and PE, linoleate was the most abundant FA, palmitate was the next, and oleate, linolenate, stearate, and ricinoleate were minor FA. The activities of oleoyl-12-hydroxylase, oleoyl-12-desaturase seem unaffected by the FA at the sn-1 position of 2-oleoyl-PC. The FA in the sn-1 position of PC does not significantly affect the activity of phospholipase A2, whereas ricinoleate is preferentially removed from the sn-2 position of PC. The results show that (i) [14C]oleate is most actively incorporated to form 2-oleoyl-PC, the immediate substrate of oleoyl-12-hydroxylase; (ii) 2-ricinoleoyl-PC is formed mostly by the hydroxylation of 2-oleoyl-PC, not from the incorporation of ricinoleate into 2-ricinoleoyl-PC; and (iii) 2-oleoyl-PE is less actively formed than 2-oleoyl-PC.

Carbon Radioisotopes↗
PubMed1997

Stearic acid modifies very low density lipoprotein lipid composition and particle size differently from shorter-chain saturated fatty acids in cultured rat hepatocytes.

Stearic acid as compared to myristate, palmitate, or oleate is poorly incorporated into triacylglycerol, a major lipid component of very low density lipoprotein (VLDL). The present study investigated the effects of these fatty acids on VLDL metabolism in cultured rat hepatocytes. All fatty acids stimulated [2-3H] glycerol incorporation into VLDL lipids and secretion of [3H]-labeled VLDL by hepatocytes. However, the rate of [3H]-labeled VLDL secretion in the presence of nonlabeled stearate (12.8 +/- 0.7 pmol/mg protein/4 h) was 46, 59, and 22% of that observed for those treated with myristate, palmitate, and oleate, respectively. [1-14C]Stearate as a substrate was also less effective than other labeled fatty acids to be incorporated into VLDL lipids. Of total VLDL lipids synthesized from [1-14C] stearate, triacylglycerol accounted for 78% as compared to 88-97% of that derived from palmitate, myristate, and oleate. The amounts of apoB100 and apoB48 were the same in hepatocytes treated with or without exogenous fatty acids. Similarly, the rate of apoB synthesis from [35S] methionine was not affected by exogenous fatty acids. The treatment of cells with various saturated fatty acids increased the particle size of VLDL to different extents. The largest particles of VLDL, with a mean diameter of 79.3 +/- 11.9 nm, were seen in the cells treated with stearate, followed by those treated with palmitate and myristate (45.5 +/- 9.8 and 38.6 +/- 6.8 nm, diameter, respectively). Clearly, hepatocytes treated with stearate secrete less VLDL and produce larger VLDL particles than those treated with shorter-chain saturated fatty acids.

Animals↗
PubMed1989

Induction of an endothermic transition in the Arrhenius plot of fatty acid uptake by lipid-depleted ascites tumor cells.

Cultured ascites tumor cells and their lipid-depleted variants containing 35-40% less membrane phospholipid and cholesterol were used to study uptake and metabolism of fatty acids complexed to albumin. Uptake of stearate and oleate at 37 degrees C was considerably higher in the lipid-depleted cells, but no significant difference in the affinity constants for stearate uptake of 3.70 microM for the lipid-depleted and 2.50 microM for the control cells was observed. Similar rates of uptake of both cultures were observed at lower temperatures up to 30 degrees C. The drastic increase in stearate uptake above 30 degrees C resulted in an endothermic transition in the Arrhenius plot with an activation energy of 20.8 kJ/mol versus 6.5 kJ/mol for the control cells. Uptake of stearate and oleate of the control cells was only slightly reduced by metabolic inhibitors, which was similar to stearic acid transport in the lipid-depleted variants. However, oleate uptake was substantially decreased in these variants. Incorporated stearate was esterified to about 50% in both cultures, and oleate between 85 and 90%. Mainly triacylglycerols and phospholipids with phosphatidylcholine (41%) and phosphatidylethanolamine (35%) as major polar lipid components, and also lower acylglycerols and cholesterol were found to be labeled. Under lipid-depleted conditions, a pronounced increase in the relative proportion of oleate incorporation into triacylglycerols was determined. It is suggested that fatty acid uptake is controlled by the number of active sites of the putative transport protein, which increases upon lipid depletion as shown from the V values. This increase may result from the segregation of membrane-bound proteins into domains (Haeffner et al. (1986) Cell Mol. Biol. 32, 359-368), which are known to be formed as a consequence of lipid phase separation in the lipid-depleted cells.

Animals↗
PubMed1990

The effect of dust-suppressant additives on the physical properties of an irreversible hydrocolloid.

The effects of dust-suppressant additives on certain physical properties of an irreversible hydrocolloid were studied in five test specimens formulated as follows: no additives (F0); 10% Duomeen cationic surfactant in 0.5% paraffin with 0.05% zinc stearate (F1); 10% Duomeen in 0.5% paraffin with 0.10% zinc stearate (F2); 20% Duomeen in 0.5% paraffin with 0.05% zinc stearate (F3); and 20% Duomeen in 0.5% paraffin with 0.10% zinc stearate (F4). The properties tested according to ADA specifications were mixing time, setting time, compressive strength, strain in compression, and permanent deformation under fixed strain. For each property, the variances between formulations were not significantly different (Levene p less than 0.05) whereas means were significantly different for stress (ANOVA p + 0.0001; Kruskal-Wallis p = 0.0019); strain (ANOVA p = 0.0003; Kruskal-Wallis p = 0.0228); deformation (ANOVA p = 0.0166; Kruskal-Wallis p = 0.0308). For the properties stress, strain, and permanent deformation under fixed strain, the paired differences of dust suppressants were established by using Duncan's multiple range test. Duomeen, instead of zinc stearate seems to be responsible for these effects.

Alginates↗
PubMed1987

Dietary vitamins A and E influence retinyl ester composition and content of the retinal pigment epithelium.

Experiments were conducted to determine the influence of dietary levels of vitamin A and alpha-tocopherol on the amounts and composition of retinyl esters in the retinal pigment epithelium of light-adapted albino rats. Groups of rats were fed diets containing alpha-tocopherol and either no retinyl palmitate, adequate retinyl palmitate, or excessive retinyl palmitate. Other groups of rats received diets lacking alpha-tocopherol and containing the same three levels of retinyl palmitate. Retinoic acid was added to diets lacking retinyl palmitate. After 27 weeks, the animals were light-adapted to achieve essentially total visual pigment bleaches, and the neural retinas and retinal pigment epithelium-eyecups were then dissected from each eye for vitamin A ester determinations. Almost all of the retinyl esters were found in the retinal pigment epithelium-eyecup portions of the eyes, mainly as retinyl palmitate and retinyl stearate. Maintaining rats on a vitamin A-deficient, retinoic acid-containing diet led to significant reductions in retinal pigment epithelial retinyl ester levels in rats fed both the vitamin E-supplemented and vitamin E-deficient diets; contrary to expectations, the effect of dietary vitamin A deficiency was more pronounced in the vitamin E-supplemented rats. Vitamin A deficiency in retinoic acid-maintained animals also led to significant reductions in retinyl palmitate-to-stearate ester ratios in the retinal pigment epithelia of both vitamin E-supplemented and vitamin E-deficient rats. Excessive dietary intake of vitamin A had little, if any, effect on retinal pigment epithelial retinyl ester content or composition. Vitamin E deficiency resulted in significant increases in retinal pigment epithelial retinyl palmitate content and in palmitate-to-stearate ester ratios in rats fed all three levels of vitamin A, but had little effect on retinal pigment epithelial retinyl stearate content. In other tissues, vitamin E deficiency has been shown to lower vitamin A levels, and it is widely accepted that this effect is due to autoxidative destruction of vitamin A. The increase in retinal pigment epithelial vitamin A ester levels in response to vitamin E deficiency indicates that vitamin E does not regulate vitamin A levels in this tissue primarily by acting as an antioxidant, but rather may act as an inhibitor of vitamin A uptake and/or storage. The effect of vitamin E on pigment epithelial vitamin A levels may be mediated by the vitamin E-induced change in retinyl palmitate-to-stearate ratios.

Animals↗
PubMed2006

Structure of montmorillonite cointercalated with stearic acid and octadecylamine: modeling, diffraction, IR spectroscopy.

Structural analysis of Na-montmorillonite co-intercalated with octadecylamine and stearic acid was carried out using combination of experiment: X-ray powder diffraction and IR spectroscopy with molecular modeling (force field calculations) in Cerius(2) modeling environment. Results of structure analysis revealed the chemical reaction of guest compounds leading to the formation of octadecylammonium stearate. This reaction may occur even before the intercalation out of the interlayer space of montmorillonite. The presence of octadecylammonium stearate in the samples was clearly confirmed by IR spectroscopy and X-ray diffraction. Present results also showed that: (1) Stearic acid itself does not intercalate into Na-montmorillonite; (2) cointercalation with octadecylamine led to the formation of octadecylammonium stearate, which was successfully intercalated into the interlayer space of montmorillonite, and (3) Na-montmorillonite intercalated with octadecylammonium stearate does not create a stable structure. Intercalated samples in ambient conditions undergo gradual decomposition, accompanied by the release of octadecylammonium stearate from the interlayer space and rearrangement of the interlayer structure. Co-intercalation of STA and ODA to lower the octadecylamine content and consequently to suppress the unfavorable effect of amine groups on the polymer matrix in nanocomposite, was investigated.

Journal Article↗
PubMed2000

Influence of fatty acid chain length and cis/trans isomerization on postprandial lipemia and factor VII in healthy subjects (postprandial lipids and factor VII).

Exaggerated postprandial lipemia is believed to be atherogenic and to influence risk of thrombosis. The postprandial effects on plasma triacylglycerol concentration, factor VII coagulant activity (FVII(c)) and activated FVII concentration (FVII(a)) of five high fat meals (5.2 MJ, 90 g fat) enriched with medium triacylglycerols (MCT, 8:0+10:0), palmitate(16:0), stearate (18:0), elaidate(18:1 trans) and oleate(18:1 cis) were compared with those following a low fat meal (5.2 MJ,10 g fat) in 16 healthy subjects using a randomized crossover design. Postprandial lipemia measured as the area under the curve (AUC arbitrary units) for plasma triacylglycerol concentration (mean+/-SE) was greater following the oleate (5.8+/-1. 05), elaidate (4.3+/-0.79) and palmitate (4.1+/-0.64) meals compared with stearate (2.0+/-0.45) and MCT (1.1+/-0.47) meals. Fatty acid analyses of the chylomicron lipids suggested that approximately one fifth of the dietary stearate was not absorbed. FVII(c) increased following the oleate, elaidate and palmitate meals and fell following the low fat meal; the increase in FVII(c) was correlated with the AUC for plasma TAG (r=0.34; P=0.001). FVII(a) concentration increased following all high fat meals but not following the low fat meal. The increase in FVII(a) at 7 h was greater after the oleate meal than after the stearate and MCT meals. These results do not support the hypothesis that dietary stearate and elaidate are responsible for the postprandial increases in FVII associated with high fat intakes.

Adolescent↗
PubMed2000

An investigation into the use of stepwise isothermal high sensitivity DSC as a means of detecting drug-excipient incompatibility.

The use of stepwise isothermal high sensitivity differential scanning calorimetry (HSDSC) as a novel means of detecting excipient incompatibility is described using aspirin mixes with magnesium stearate and stearic acid as model systems. Aspirin, magnesium stearate and stearic acid alone and as mixes were studied in scanning mode using conventional DSC and were then subjected to a stepwise heating programme using HSDSC, whereby the samples were heated to temperatures between 45 and 70 degrees C and held for 1 h, during which the heat flow to or from the sample was measured. The data indicated that while no thermal events were detected for the individual components or mixes with stearic acid other than melting of stearic acid, 50% w/w mixes of magnesium stearate showed a marked endothermic response at temperatures above 55 degrees C. The data were fitted to an adaptation of an existing kinetic model for the degradation process and a reasonable correlation found. Mixes of the drug with the two excipients were then studied at 60 degrees C over 6 h at concentrations between 1 and 50% w/w. Incompatibilities with magnesium stearate concentrations as low as 1% w/w could be detected using this approach. Compacts of magnesium stearate and aspirin were also studied, with considerably more pronounced thermal events taking place compared to the powder mixes. It is concluded from these studies that while the study has highlighted certain limitations of the approach, stepwise isothermal DSC represents a potentially highly useful means of detecting excipient incompatibilities.

Aspirin↗
PubMed2001

Formulation and process optimization to eliminate picking from market image tablets.

A tablet formulation when compressed using market image tooling may cause picking of powder. A D-optimal statistical experiment was designed to optimize the direct compression formulation and the process to alleviate picking of powder. The effects of levels of magnesium stearate, colloidal silicon dioxide (CSD), and lubrication time on picking were investigated using original compression tooling. These optimization results provided a small robust manufacturing region, hence a change in the cut angles of embossed letters and numbers from 70 degrees to 90 degrees in the modified compression tooling was evaluated. A statistical analysis of the data identified a robust manufacturing region that included formulations containing magnesium stearate 1-1.25% w/w, CSD 0.1-0.3% w/w, with a lubrication time of 5-10 min when compressed using modified compression tooling. The results indicate a significant reduction in picking by increasing the cut angles of embossed letters and numbers in the modified compression tooling. By evaluating interactions between various variables, we demonstrate a concentration dependent effect of CSD on the lubrication efficiency of magnesium stearate and compactability of microcrystalline cellulose containing formulation. In addition, the lubrication efficiency of magnesium stearate is maintained by blending CSD with powder blend prior to lubrication with magnesium stearate.

Drug Compounding↗
PubMedDate not supplied

Amphotericin B encapsulated in micelles based on poly(ethylene oxide)-block-poly(L-amino acid) derivatives exerts reduced in vitro hemolysis but maintains potent in vivo antifungal activity.

The core-forming blocks of amphiphilic diblock copolymers based on methoxypoly(ethylene oxide)-block-poly(L-aspartate), PEO-b-p(L-Asp), were derivatized to incorporate stearate side chains. The effects of stearate esterification were assessed in terms of micelle stability and amphotericin B (AmB) encapsulation/release. The level of stearate esterification modulates the relative self-aggregation state of encapsulated AmB as evidenced by absorption spectroscopy. When AmB is physically loaded into polymeric micelles, the onset of hemolytic activity toward bovine erythrocytes is delayed relative to that of the free drug. Furthermore, the extent of esterification (0, 46, or 91%) appears to have profound influence on the time-dependent hemolytic profile of AmB toward bovine erythrocytes. Particularly in the case of highly substituted stearate ester micelles, incomplete and gradual build-up of hemolysis was observed over a period of 24 h. On the basis of the corresponding absorption spectra, we speculate that encapsulated AmB may interact strongly with stearate side chains, resulting in sustained release. In a neutropenic murine model of disseminated candidiasis, kidney colony-forming unit determination revealed dose-dependent efficacy for the polymeric micelle/AmB formulation, which was not significantly different from that of Fungizone at doses of 0.2, 0.3, and 0.6 mg/kg (p = 0.7). Thus, AmB administered via a polymeric micelle formulation retained potent in vivo activity.

Amphotericin B↗
PubMed1988

Fatty acid specificity for the synthesis of triacylglycerol and phosphatidylcholine and for the secretion of very-low-density lipoproteins and lysophosphatidylcholine by cultures of rat hepatocytes.

1. The synthesis and secretion of glycerolipids by monolayer cultures of rat hepatocytes was measured by using radioactive choline, glycerol and fatty acids and by measuring the concentration of triacylglycerols in the cells. 2. The incorporation of glycerol into triacylglycerol and the accumulation of this lipid in hepatocytes showed little specificity for fatty acids, except for eicosapentaenoate, which stimulated least. Oleate was more effective at stimulating triacylglycerol secretion than were palmitate, stearate, arachidonate and eicosapentaenoate. 3. Linoleate, linolenate, arachidonate and eicosapentaenoate stimulated the incorporation of glycerol and choline into phosphatidylcholine that was secreted into the medium. By contrast, palmitate and stearate produced relatively high incorporations into the phosphatidylcholine that remained in the cells. 4. The incorporation of glycerol and choline into lysophosphatidylcholine in the medium was stimulated 2-3-fold by all of the unsaturated fatty acids tested, whereas palmitate and stearate failed to stimulate if the acids were added separately. When 1 mM-stearate was added with 1 mM-linoleate, the incorporation of linoleate into lysophosphatidylcholine was about 4 times higher than that of stearate. 5. It is proposed that the secretion of lysophosphatidylcholine by the liver could provide a transport system for choline and essential unsaturated fatty acids to other organs.

Animals↗
PubMed1994

The fatty acids in unremodelled trypanosome glycosyl-phosphatidylinositols.

Glycolipid A, the precursor of the glycosyl-phosphatidylinositol (GPI) anchor of the trypanosome variant surface glycoprotein, is constructed in two phases. First, the glycan is assembled on phosphatidylinositol (PI), yielding a glycolipid termed A'. Second, glycolipid A' undergoes fatty acid remodelling, by deacylation and reacylation, to become the dimyristoyl species glycolipid A. In this paper, we examine the fatty acid content of glycolipid A' and its cellular progenitors. A' contains exclusively stearate at the sn-1 position and a complex mixture of fatty acids (including 18:0, 18:1, 18:2, 20:4 and 22:6) at sn-2. Presumably these fatty acids derive from stearate-containing PI species which initially enter the biosynthetic pathway. We compared the diacylglycerol species from glycolipid A' with those from phosphatidylinositol to determine whether a subset of stearate-containing PIs is utilized for GPI biosynthesis. We found that the spectrum of stearate-containing diacylglycerols in PI is similar to that in A', although the proportions of each compound differ. Total PI in general was highly enriched in stearate-containing species. Differences in composition between glycosylated PI and total cellular PI may be due to the substrate specificity of the sugar transferase which initiates the GPI biosynthetic pathway. Alternatively, the species of PI present at the endoplasmic reticulum site of GPI biosynthesis may differ from those in total PI.

Animals↗
PubMed1998

Fatty acid cycling in human hepatoma cells and the effects of troglitazone.

Fatty acid cycling by chain shortening/elongation in the peroxisomes is an important source of fatty acids for membrane lipid synthesis. Its role in the homeostasis of nonessential fatty acids is poorly understood. We report here a study on the cycling of saturated fatty acids and the effects of troglitazone in HepG2 cells in culture using [U-13C]stearate or [U-13C]oleate and mass isotopomer analysis. HepG2 cells were grown in the presence of 0.7 mmol/liter [U-13C]stearate or [U-13C]oleate, and in the presence and absence of 50 microM troglitazone for 72 h. Fatty acids extracted from cell pellets after saponification were analyzed by gas chromatography/mass spectrometry. Peroxisomal beta-oxidation of uniformly 13C-labeled stearate (C18:0) and oleate (C18:1) resulted in chain shortening and produced uniformly labeled palmitate (C16:0) and palmitoleate (C16:1). In untreated cells, 16% of C16:0 was derived from C18:0 and 26% of C16:1 from C18:1 by chain shortening. Such contributions were significantly increased by troglitazone to 23.6 and 36.6%, respectively (p < 0.001). Desaturation of stearate contributed 67% of the oleate, while reduction of oleate contributed little to stearate (2%). The desaturation of C18:0 to C18:1 was not affected by troglitazone. Our results demonstrated a high degree of recycling of C18:0 and C18:1 to C16:0 and C16:1 through chain shortening and desaturation. Chain shortening was accompanied by chain elongation in the synthesis of other long chain fatty acids. Troglitazone specifically increased recycling by peroxisomal beta-oxidation of C18 to C16 fatty acids, and the interconversion of long chain fatty acids was associated with reduced de novo lipogenesis.

Carcinoma, Hepatocellular↗
PubMed2000

Regulation of Tiam1 nucleotide exchange activity by pleckstrin domain binding ligands.

Rho family GTPases play roles in cytoskeletal organization and cellular transformation. Tiam1 is a member of the Dbl family of guanine nucleotide exchange factors that activate Rho family GTPases. These exchange factors have in common a catalytic Dbl homology and adjacent pleckstrin homology domain. Previous structural studies suggest that the pleckstrin domain, a putative phosphoinositide-binding site, may serve a regulatory function. We identified ascorbyl stearate as a compound that binds to the pleckstrin domain of p120 Ras GTPase-activating protein. Furthermore, ascorbyl stearate appears to be a general pleckstrin domain ligand, perhaps by mimicking an endogenous amphiphilic ligand. Tiam1 nucleotide exchange activity was greatly stimulated by ascorbyl stearate. Certain phosphoinositides also stimulated Tiam1 activity but were less potent than ascorbyl stearate. Tiam1 contains an additional N-terminal pleckstrin domain, but only the C-terminal pleckstrin domain was required for activation. Our results suggest that the pleckstrin domains of Dbl-type proteins may not only be involved in subcellular localization but may also directly regulate the nucleotide exchange activity of an associated Dbl homology domain. In addition, this paper introduces ascorbyl stearate as a pleckstrin domain ligand that can modulate the activity of certain pleckstrin domain-containing proteins.

Animals↗
PubMed2004

Effect of different dispersing agents on the characteristics of Eudragit microspheres prepared by a solvent evaporation method.

Eudragit RS microspheres containing verapamil HCl for oral use were prepared using three different dispersing agents: aluminium tristearate, magnesium stearate and sucrose stearate, by a solvent evaporation method. The effects of the type and concentration of the dispersing agents and the inner phase polymer concentration on the size and T63.2%, (the time at which 63.2% of the drug is released) of microspheres were determined by multiple linear regression analysis. The morphology of microspheres was characterized by scanning electron microscopy. The surface of microspheres prepared with sucrose stearate was smoother and non-porous and the drug release from these microspheres was the fastest. When aluminium tristearate or magnesium stearate were used as dispersing agents, the particle size of microspheres became smaller. Increasing amounts of these two dispersing agents led to the accumulation of their free particles onto the surfaces of the microspheres. The drug release from the microspheres was slower than that of the microspheres from sucrose stearate depending on their hydrophobic structures. According to the results of the multiple linear regression analysis among the dispersing agents used, aluminium tristearate showed the best correlation between the examined input (dispersing agent and polymer concentrations) and output (T63.2%. and particle size) variables.

Acrylic Resins↗
PubMed2005

Press chamber coating as external lubrication for high speed rotary presses: lubricant spray rate optimization.

Lubrication of the tooling (punches and dies) is necessary to produce tablets. The most commonly used lubricant is magnesium stearate. Adding and blending magnesium stearate to the tablet mass often has negative effects on the properties of the compressed tablets (e.g., decreasing the tensile strength of the tablet). To avoid these negative effects, external lubrication systems were developed. This study investigated the functionality and the influence of a new press chamber coating system called the PKB II. The major difference between the PKB II and previous systems is its ability to spray a mixture of powdered magnesium stearate and air directly onto the punches and dies which was determined to allow the running of the rotor at higher speeds. The data showed a clear correlation between the spray rate of the lubricant and the concentration of the magnesium stearate per tablet. The PKB II was designed to allow for adjustments, in order to optimize the spray rate, by using the ejection force. The concentration of magnesium stearate was reduced to approximately 0.04% per tablet, using the PKB II. Additionally, the most common negative effects, such as the decrease in tablet tensile strength, were avoided by using this system.

Calibration↗
PubMed2002

Roller compaction and tabletting of St. John's wort plant dry extract using a gap width and force controlled roller compactor. II. Study of roller compaction variables on granule and tablet properties by a 3(3) factorial design.

The purpose of this study was to investigate the influence of roller compaction parameters and the amount of magnesium stearate used in dry granulation on granule and tablet properties of a dry herbal extract from St. John's wort (Hypericum perforatum L.). Two different extract batches were blended with magnesium stearate and compacted using a gap width and force controlled roller compactor. A 3(3) factorial design was used to evaluate the influence of the three independent variables, the amount of magnesium stearate, the roller compaction force, and the granulating sieve size on the mean particle size of granulated extracts and on the disintegration time of tablets containing these granulated extracts. The evaluation was done by multilinear stepwise regression analysis. The mean particle size d50 (R2 > 0.9) of both compacted extracts increased with increasing compaction force and with granulating sieve size. The disintegration time of the tablets was mostly in the range 5-15 min and increased slightly with increasing magnesium stearate concentration in the compacted extract and with decreasing compaction force of the roller compaction. The incorporation of magnesium stearate into the granulated extract reduced its potential negative influence on the disintegration time, while maintaining its functionality as a lubricant.

Compressive Strength↗