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At least 793 records · Page 44Linked to original sources
PubMed2004

Characterization of caprylocaproyl macrogolglycerides based microemulsion drug delivery vehicles for an amphiphilic drug.

Microemulsion systems composed of water, isopropyl myristate, PEG-8 caprylic/capric glycerides (Labrasol), and polyglyceryl-6 dioleate (Plurol Oleique), were investigated as potential drug delivery vehicles for an amphiphilic model drug (diclofenac diethylamine). Pseudo-ternary phase diagram of the investigated system, at constant surfactant/cosurfactant mass ratio (Km 4:1) was constructed at room temperature by titration, and the oil-to-surfactant/cosurfactant mass ratios (O/SC) that exhibit the maximum in the solubilization of water were found. This allowed the investigation of the continuous structural inversion from water-in-oil to oil-in-water microemulsions on dilution with water phase. Furthermore, electrical conductivity (sigma) of the system at Km 1:4, and O/SC 0.250 was studied, and the percolation phenomenon was observed. Conductivity and apparent viscosity (eta') measurement results well described colloidal microstructure of the selected formulations, including gradual changes during their formation. Moreover, sigma, eta', and pH values of six selected microemulsion vehicles which differ in water phase volume fraction (phi(w)) at the selected Km and O/SC values, were measured. In order to investigate the influence of the amphiphilic drug on the vehicle microstructures, each system was formulated with 1.16% (w/w) diclofenac diethylamine. Electrical conductivity, and eta' of the investigated systems were strongly affected by drug incorporation. The obtained results suggest that diclofenac diethylamine interacts with the specific microstructure of the investigated vehicles, and that the different drug release kinetics from these microemulsions may be expected. The investigated microemulsions should be very interesting as new drug carrier systems for dermal application of diclofenac diethylamine.

Administration, Cutaneous↗
PubMed2004

Self-emulsifying pellets prepared by wet granulation in high-shear mixer: influence of formulation variables and preliminary study on the in vitro absorption.

A method of producing self-emulsifying pellets by wet granulation of powder mixture composed of microcrystalline cellulose, lactose and nimesulide as model drug with a mixture containing mono- and di-glycerides, polisorbate 80 and water, in a 10-l high shear mixer has been investigated. The effects of the formulation variables on pellets characteristics were evaluated by mixtures experimental design and by a polynomial model, in order to describe the phenomenon, to verify eventual interactions among components of the mixture and to investigate the feasibility of scaling-up. After determination of size distribution, the pellets were characterised by scanning electron microscopy, dissolution and disintegration tests, and by in vitro absorption test Such an approach, applied to the development of a self-emulsifying system for nimesulide as poorly water-soluble model drug, resulted in different formulations with improved drug solubility and permeability characteristics. The data demonstrate that pellets composed of oil to surfactant ratio of 1:4 (w/w) presented improvement in performance in permeation experiments.

Absorption↗
PubMed2005

In vitro release of diclofenac diethylamine from caprylocaproyl macrogolglycerides based microemulsions.

The purpose of the present study was to determine the influence of both formulation parameters and vehicle structure on in vitro release rate of amphiphilic drug diclofenac diethylamine (DDA) from microemulsion vehicles containing PEG-8 caprylic/capric glycerides (surfactant), polyglyceryl-6 dioleate (cosurfactant), isopropyl myristate and water. From the constructed pseudo-ternary phase diagram at surfactant-cosurfactant mass ratio (K(m) 1:1), the optimum oil-to-surfactant-cosurfactant mass ratio values (O/SC 0.67-1.64) for formulation of microemulsions with similar concentrations of hydrophilic, lipophilic and amphiphilic phases (balanced microemulsions) were found. The results of characterization experiments indicated bicontinuous or nonspherical water-continuous internal structure of the selected microemulsion vehicles. Low water/isopropyl myristate apparent partition coefficient for DDA as well as elevated electrical conductivity and apparent viscosity values for the investigated microemulsion formulations containing 1.16% (w/w) of DDA, suggested that the drug molecules was predominantly partitioned in the water phase and most likely selfaggregate and interact with interfacial film. Release of DDA from the selected water-continuous (W/O), oil-continuous (O/W) and balanced microemulsions was investigated using rotating paddle dissolution apparatus modified by addition of enhancer cell. A linear diffusion of DDA through regenerated cellulose membrane was observed for the W/O and O/W formulations with the low content of dispersed phase. Non-linearity of the drug release profile in the case of bicontinuous formulations was related to the more complex distribution of DDA including interactions between the drug and vehicle. The membrane flux value increases from 25.02 microgcm(-2)h(-1) (W/O microemulsion) to 117.94 microgcm(-2)h(-1) (O/W microemulsion) as the water phase concentration increases. Moreover, the obtained flux values for balanced microemulsions (29.38-63.70 microgcm(-2)h(-1)) suggested that bicontinuous microstructure hampers the release of the amphiphilic drug.

Diclofenac↗
PubMed2006

Preparation and evaluation of oral solid heparin using emulsifier and adsorbent for in vitro and in vivo studies.

Oral anticoagulant therapy with heparin has been challenged by formulating heparin in oral solid preparation. As heparin, low molecular weight heparin (LMWH) was used. LMWH was dispersed with a surfactant used for the self-microemulsifying drug delivery system (SMEDDS), PEG-8 caprylic/capric glycerides (Labrasol), and the mixture was solidified with three kinds of adsorbents, microporous calcium silicate (Florite RE), magnesium alminometa silicate (Neusilin US(2)) and silicon dioxide (Sylysia 320). The in vitro release study showed that the T50%s were 3.2+/-0.1min for Sylysia 320, 4.6+/-0.2min for Florite RE, 13.7+/-0.1min for Neusilin US(2). The in vivo rat absorption study showed that Florite RE system had the highest C(max), 0.42+/-0.01IU/mL and AUC, 0.59+/-0.06IUh/mL, where plasma LMWH levels were measured as anti-Xa activity. Other preparations had the C(max) and AUC, 0.12+/-0.01IU/mL and 0.15+/-0.02IUh/mL for Neusilin US(2) and 0.25+/-0.02IU/mL and 0.40+/-0.03IUh/mL for Sylysia 320, respectively. The bioavailability (BA) of LMWH from the microporous calcium silicate preparation, Florite RE, was 18.8% in rats by comparing the AUC obtained after i.v. injection of LMWH, 40IU/kg to another group of rats. Florite RE system was evaluated in dogs after oral administration in an enteric capsule made of Eudragit S100 at the LMWH dose of 200IU/kg. High plasma anti-Xa activity levels were obtained, i.e., the C(max) was 0.48+/-0.11IU/mL and AUC was 1.64+/-0.32IUh/mL. These results suggest that adsorbent system is useful as an oral solid delivery system of poorly absorbable drugs such as LMWH.

Administration, Oral↗
PubMed1981

A simpler approach to labor induction using lipid-based prostaglandin E2 vaginal suppository.

The outcome of labor induced by use of a glyceride-based vaginal suppository of prostaglandin E2 (PGE2) inserted 3 hours before amniotomy, when the cervix is favorable, has been assessed. Using 5 mg PGE2 for primigravidas and 2.5 mg for multigravidas, 63% of the former and 81% of the latter established labor and were delivered of their infants without oxytocin augmentation, allowing ambulation during early labor. No maternal complications were detected as a result of the PGE2 treatment. Compared with patients undergoing conventional induction by amniotomy and immediate oxytocin titration there was no difference in the duration of labor, with a few patients establishing labor and giving birth quickly with both induction methods. Fetal distress was less common following PGE2 treatment than following conventional induction, with three patients in each group requiring delivery by cesarean section. Cephalopelvis disproportion in the second stage of labor requiring cesarean section to deliver occurred more frequently in the prostaglandin-treated group, possibly as a result of reduced upper segment contractility in the first stage of labor with subsequent poor fetal head molding. Epidural analgesia and postpartum hemorrhge were both reduced following PGE2-induced labor.

Adult↗
PubMed1981

Dissolution of retained duct stones by perfusion with monooctanoin via a Teflon catheter introduced endoscopically.

Retained bile duct stones in patients who have undergone prior cholecystectomy are removed by operation or endoscopic sphincterotomy. We achieved dissolution of cholesterol duct stones by perfusion with monooctanoin, a commercially available mixture of medium chain glycerides. Sixteen patients were treated in whom endoscopic sphincterotomy was impossible or unsuccessful. In 12 patients, 16 stones were dissolved within 6 to 25 days (mean, 15.6 days). In all successfully treated patients elevated serum liver enzymes became normal during therapy.

Aged↗
PubMed1978

Fat digestion in the stomach of premature infants. I. Characteristics of lipase activity.

Lipolytic activity was studied in gastric aspirates of 13 premature infants of birth weight 1,050 to 1,786 gm. All infants received a diet of infant formula fed by gastric tube. Gastric aspirates were collected after irrigating the stomach with 2 to 5 ml sterile saline before regular feeding. Lipolytic activity, tested with doubly labeled 3H glyceryl-14 C tripalmitin substrate, was 55.6 +/- 11.7 n mol/min/ml (range 4.2 to 140). The lipolytic activity had a pH optimum of 5.4 and produced partial glycerides (mono and diglycerides), glycerol, and free fatty acids. Lipolysis was inhibited by bile salts. Our findings show that in premature infants, as in adults, digestion of dietary fat starts in the stomach. Since bile salt concentrations are low in premature infants, the amphiphilic reaction products formed (monoglyceride and FFA) could play a significant role in the stabilization of lipid emulsions.

Digestion↗
PubMed1999

Development of a rectal nicotine delivery system for the treatment of ulcerative colitis.

The aims of this investigation were: i. to develop a rectal nicotine delivery system with bioadhesives for the treatment of ulcerative colitis and ii. to evaluate nicotine transport and cytotoxicity of the delivery system using Caco-2 cell culture systems. Rectal nicotine suppository formulations were prepared in semi-synthetic glyceride bases (Suppocire AM and AI, Gattefosse Inc.) by fusion method. The in vitro release of nicotine was carried out in modified USP dissolution apparatus 1. Differential scanning calorimetry (DSC) and powder X-ray diffraction were used to study the polymorphic changes if any in the formulations. An LC method was used for the assay of nicotine. The effect of bioadhesives (glyceryl monooleate (GMO), and Carbopol) on the nicotine flux was evaluated using Caco-2 cell permeability studies and Caco-2 cell viability was determined using the MTT toxicity assay. In vitro release studies indicated that the low melting AI base was superior to that of the AM base. Presence of GMO in the formulation enhanced the release of nicotine whereas Carbopol showed an opposite effect. The enhanced release of nicotine in the presence of GMO was found to be partly due to the melting point lowering effect of this compound. Caco-2 cell absorption studies showed that there was a decrease in the flux of nicotine in the presence of both the bioadhesives. The flux of the fluorescein marker which is used to study the integrity of the cell monolayers was found to be slightly higher only in the presence of 10% (w/w) Carbopol. Nicotine, Carbopol, and GMO do not have any cytotoxic effect on these cell monolayers within the concentration range used in the formulations. Rectal nicotine formulations containing bioadhesives were developed and characterized. Both in vitro release and cell culture studies have indicated that one can manipulate the nicotine release from these rectal delivery systems by incorporation of various bioadhesives or the use of different bases in the formulation. Nicotine concentration below 2% (w/v) and bioadhesive concentration below 10% (w/w) do not have any cytotoxic effect on Caco-2 cells.

Acrylic Resins↗
PubMed1996

Bioavailability of cyclosporine in rats after intragastric administration: a comparative study of the L2-phase and two other lipid-based vehicles.

The purpose of this study was to evaluate formulations based on surface active dietary lipids only as oral vehicles for cyclosporine. The absolute bioavailability of cyclosporine from two new lipid vehicles was determined in rats after intragastric administration and compared to that of Sandimmun oral solution, which contains non-ionic surface active substances in addition to dietary lipids. In the new vehicles, cyclosporine was dissolved in two different mixtures of glycerides from long-chained fatty acids. One mixture forms an L2-phase, an oil with very low interfacial tension towards water, and was administered both as the oily L2-phase and as a predispersed emulsion formulation. The other mixture forms a liquid crystalline phase and was administered only as an aqueous dispersion. The mean bioavailability of cyclosporine from Sandimmun was 8% while it was 34% from the L2-phase, 38% from the predispersed L2-phase and 27% from the dispersed liquid crystalline phase. The coefficients of variation in area under the blood concentration curve after administration of the two formulations based on the L2-phase were quite low (31% for the L2-phase and 24% for the predispersed L2-phase) and comparable to that after intravenous administration (24%), while the dispersed liquid crystalline phase gave a higher variability (91%), comparable to that of Sandimmun oral solution (101%). The low variabilities found with the two L2-phase vehicles suggest that this formulation is "self-emulsifying' in the gastrointestinal tract. Since the L2-phase is based on dietary lipids only, it is expected to be well tolerated and could prove to be a good vehicle for long-term clinical use of oral cyclosporine.

Administration, Oral↗
PubMedDate not supplied

Characteristics of immobilized lipase on hydrophobic superparamagnetic microspheres to catalyze esterification.

A novel immobilized lipase (from Candida rugosa) on hydrophobic and superparamagnetic microspheres was prepared and used as a biocatalyst to catalyze esterification reactions in diverse solvents and reaction systems. The results showed that the immobilized lipase had over 2-fold higher activities in higher log P value solvents. An exponential increase of lipase activity against log P of two miscible solvent mixtures was observed for the first time. Both free and immobilized lipase achieved its maximum activity at the range of water activity (a(w)) 0.5-0.8 or higher. At a(w) 0.6, the immobilized lipase exhibited markedly higher activities in heptane and a solvent-free system than did the native lipase. In multicompetitive reactions, the alcohol specificity of the lipase showed a strong chain-length dependency, and the immobilized enzyme exhibited more preference for a longer-chain alcohol, which is different from previous reports. The immobilized lipase showed higher specificities for butyric acid and the medium-chain-length fatty acids (C(8)-C(12)). Then, the immobilized lipase was extended to solvent-free synthesis of glycerides from glycerol and fatty acids. Recovered by magnetic separation, the immobilized lipase exhibited good reusability in repeated batch reaction, indicating its promising feature for biotechnology application.

Adsorption↗
PubMed2006

Efficient hydrolysis of tuna oil by a surfactant-coated lipase in a two-phase system.

A surfactant-coated lipase (SCL) prepared by mixing Candida rugosa lipase with emulsifier in ethanol was used to hydrolyze tuna oil in a two-phase aqueous-organic system. Both enzyme (SCL) and substrate (tuna oil) were soluble in the organic phase, and the hydrolysis could occur with water molecules from the aqueous phase. This hydrolysis could promptly proceed compared to that catalyzed by native lipases which only occurred at the interface between the two phases. Michaelis-Menten kinetics in the two-phase reactions showed that the K(m) value of the SCL was half that of the native lipase, while the maximum velocity (V(max)) was 11.5 times higher. The hydrolysis method resulted in enrichment of n-3 polyunsaturated fatty acid (n-3 PUFA) content in glyceride mixtures from 26.4% to 49.8% and DHA from 19.1% to 38.9%. The SCL acted as an efficient hydrolytic catalyst for tuna oil.

Animals↗
PubMed2001

Changes in fatty acids composition during seed growth and physicochemical characteristics of oil extracted from four safflower cultivars.

Fatty acid contents at different stages of maturity and physicochemical characteristics of oil extracted from mature seeds of four safflower cultivars (S208, S400, S541, and S303) were studied. Results indicated that for all cultivars both saturated and unsaturated fatty acid contents fluctuated with seed growth and development. Palmitic acid content decreased up to day 20 after which it started to increase for the S400, S541, and S303 cultivars, while for S208 it progressively decreased. Stearic acid fluctuated with seed growth and development. Oleic acid showed slight changes with seed growth and development, while linoleic acid decreased with seed growth and development for the S400, S541, and S303 cultivars while for S208 after day 30, it started to increase significantly. For all cultivars, glyceride contents varied among the cultivars with maximum values of 97.70, 2.80 and 0.20 for tri-, di- and monoglycerides, respectively. Physicochemical investigation of mature seed oils showed that the color, density, refractive index, free fatty acids, peroxide value, saponification value and unsaponifiable matter were similar for all cultivars while viscosity, iodine value, and acetone insoluble matter varied among the cultivars.

Chemical Phenomena↗
PubMed2006

Synthesis of acylglycerols from omega-3 fatty acids and conjugated linoleic acid isomers.

n-3 PUFA (omega-3 polyunsaturated fatty acid) concentrate from mackerel oil enriched in EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) was used to esterify isomers of CLA (conjuated linoleic acid) to produce acylglycerols (glycerides). Catalysis was potentiated by immobilized lipases from the yeast Candida antarctica and the mould Mucor miehei. C. antarctica lipase showed higher reactivity and much faster initial rate of incorporation of CLA into acylglycerols than its M. miehei counterpart. Synthesis with molecular sieves also achieved a better rate of incorporation of fatty acids into acylglycerols than using vacuum or systems without water removal. Esterification achieved at 40 degrees C with C. antarctica lipase was significantly different from that achieved at 60 or 50 degrees C. However, there was no significant (P<0.05) difference between esterification at 50 degrees C and 60 degrees C. The molar ratio of glycerol to fatty acid was found to influence the initial rate of incorporation, with the lower ratios showing higher initial rates compared with the higher ratios. The present study shows that direct esterification is an effective mechanism for producing acylglycerols from fatty acids in a controlled system.

Animals↗
PubMed1967

Utilization of endogenous lipid by the isolated perfused rat heart.

1. The lipids of the rat heart have been studied with regard to amount, classes present and fatty acid composition of free fatty acids, triglycerides and phospholipids. Myocardial lipid contained 300mumoles of total fatty acid/g. dry wt. of which only 2-4mumoles were free; the remainder was esterified, chiefly as phospholipid. Neutral esters, of which triglyceride was the principal form, made up 15% of the total fatty acids. 2. When normal hearts were perfused with a nutrient-free medium until exhaustion, the triglyceride concentration declined from 43 to 13mumoles/g. dry wt. The content of phospholipids, partial glycerides and cholesteryl esters did not change. When the lipids of the rat heart were labelled with [1-(14)C]palmitate before perfusion with non-nutrient medium, radioactivity disappeared from the triglyceride, diglyceride and free fatty acid fractions, but not from the phospholipid or other ester classes. 3. These experiments support the view that only a small fraction of the total cardiac lipid, principally triglycerides and to a smaller extent diglycerides, is available as a source of fuel in the absence of exogenous substrate.

Animals↗
PubMed1970

Metabolism of endogenous sterol ester by the superovulated rat ovary in vitro.

Sterol, glyceride and phospholipid were found to account for more than 90% (w/w) of the lipid extracted from whole superovulated rat ovaries. These lipids, together with non-esterified fatty acids, were assayed in slices of the tissue after incubation for various times. Whereas the concentrations of triglyceride, diglyceride and phospholipid did not change significantly during incubation, that of sterol ester markedly decreased and those of free sterol, monoglyceride and non-esterified fatty acid increased. Evidence is presented that in this tissue (in contrast with other mammalian tissues) the main endogenous substrate for respiration is fatty acid derived from sterol ester.

Animals↗
PubMed1971

Metabolic effects of the major component of bovine growth hormone.

Bovine growth hormone, subjected to DEAE-cellulose chromatography, yielded one major and several minor components. The various chromatographic fractions of bovine growth hormone were compared with the parent material for their ability to promote hormone effects in vivo and in vitro. The major component of bovine growth hormone was homogeneous by acrylamide-gel electrophoresis, rechromatography and sedimentation equilibrium. Its amino acid composition was similar to that of the parent hormone. The major component possessed all the qualitative activities present in the original heterogeneous material, including promotion of acute hypoglycaemia and hypolipaemia. In studies in vitro in adipose-tissue segments the major component of the hormone increased entry of glucose and its oxidation to CO(2), conversion of glucose into glyceride glycerol, release of glycerol and incorporation of histidine into adiposetissue protein. Other chromatographic fractions of bovine growth hormone were not homogeneous and possessed some but not all of the metabolic activities attributed to the hormone preparations or its major component. Thus, the metabolic effects obtained with bovine growth-hormone preparations in vivo and in vitro can be obtained with the major homogeneous component of the hormone. This observation precludes the possibility that the metabolic effects obtained with bovine growth-hormone preparations are due to the combined actions of a number of components found therein.

Acrylates↗
PubMed1971

The role of the plasma membrane in fatty acid uptake by rat liver parenchymal cells.

1. Suspensions of isolated rat liver parenchymal cells incorporate [(14)C]palmitic acid into glycerides at about 40% of the rate obtained with liver slices. 2. At short time-intervals most of the incorporation is into phosphatidylcholine and this is recovered mainly in the plasma-membrane fraction. 3. At later times (5min to 2h) the [(14)C]palmitic acid is mainly found in triglyceride, but this is not recovered in the plasma-membrane fraction. 4. Addition of lysophosphatidylcholine increases incorporation of palmitic acid into both phosphatidylcholine and triglyceride, with maximum effect at about 0.1mm. 5. In vivo, 1min after injection of [(14)C]palmitic acid, radioactive phosphatidylcholine is concentrated in the plasma-membrane fraction, but the proportion present in this fraction declines rapidly. 6. The phosphatidylcholine of the plasma-membrane fraction has, at 1min after injection, a specific radioactivity 30-fold greater than that of the whole tissue. 7. This phosphatidylcholine reaches its maximum specific radioactivity before the tissue phosphatidic acid or diglyceride. 8. The phosphatidylcholine of the plasma-membrane fraction has a very rapid turnover. 9. It is proposed that the rapid formation of phospholipids in the plasma membrane is by acylation of their lyso-derivatives and the role of this process in fatty acid uptake is discussed.

Acylation↗
PubMed1974

Lipogenesis in rabbit isolated fat-cells.

1. Fat-cells isolated from rabbit perirenal adipose tissue were incubated with the following U-(14)C-labelled substrates: 5mm-glucose (+insulin), 5mm-pyruvate, 5mm-lactate, 5mm-glucose+5mm-acetate (+insulin), and the relative rates of incorporation of these substrates into glyceride fatty acids determined. In general total rates of fatty acid synthesis were similar whatever substrate was supplied to the cells. 2. Rabbit fat-cells incorporated [U-(14)C]acetate into fatty acids and CO(2) as well in the absence of glucose as in the presence of this substrate. 3. The disposition of the utilization of glucose-derived carbon through various metabolic pathways was determined. 4. Extramitochondrial and mitochondrial activities were determined for 11 enzymes. The cells contained a very low activity of pyruvate carboxylase, undetectable NADP-malate dehydrogenase activity and a high mitochondrial phosphoenolpyruvate carboxylase activity. 5. Various rabbit fat-cell metabolic parameters based on the measurement of (14)C incorporation and enzyme activity were compared with the same parameters previously measured in rat and guinea-pig fat-cells. In general guinea pig occupied a position between rat and rabbit with respect to these parameters. 6. The profiles of substrate incorporation into fatty acids and of relative enzyme activities in rabbit fat-cells indicated that the operation of a ;citrate-cleavage' pathway may not be obligatory for the supply of lipogenic acetyl units.

Acetates↗