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PubMed2004

The effect of dehydration history on PVA/PVP hydrogels for nucleus pulposus replacement.

The feasibility of the use of a copolymer gel prepared from blends of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) for endoscopic replacement of the nucleus pulposus of a lumbar intervertebral disc was examined in this study. Hydrogels were processed with the use of three freeze/thaw cycles to induce crystallinity. As-prepared samples were dehydrated to various levels: 70.4, 46.3, 25.1, and 10.3% of their as-prepared masses and subsequently rehydrated. The dehydration history controlled the dimensions upon swelling and caused distortion of the material, with major distortion occurring when the hydrogel reached around 25% of the initial hydrated mass. The dehydration history affected the mechanical behavior of the rehydrated gels. Increased dehydration resulted in increased compressive modulus for the reswollen gels. Experiments were performed to investigate the formation of a skin layer that was found on the hydrogels during the dehydration process. The skin was found to dehydrate quickly and form a barrier to further dehydration from the core. Rubber elasticity theory was used to describe the differences in the network characteristics between the skin and the core of a drying hydrogel. The dehydration/rehydration process used in this study and an implantation of a cadaver model demonstrate the feasibility of endoscopic nucleus replacement.

Biocompatible Materials↗
PubMed2006

Functional polymer hydrogels for embryonic stem cell support.

Embryonic stem (ES) cells are pluripotent cells with the ability to differentiate among all embryonic and adult cell lineages. Derivation of human ES cells opened up the way for treatment of many serious disorders by stem cell-based transplantation therapy. One of the most exciting challenges in development of transplantation therapies is to repair the damaged part of the organ or tissue by transplantation of undifferentiated ES cells or their differentiated derivatives within three-dimensional polymer scaffold. This method allows both renewal of structure and restoration of function of the organ. To address this issue, new polymer hydrogels were synthesized and tested. Cationic hydrogel slabs were synthesized by bulk radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) with ethylene dimethacrylate (EDMA) or 1-vinyl-2-pyrrolidone (VP) with N,N'-divinylethyleneurea (DVEU) or EDMA in the presence of saccharose or NaCl as a porogen. Swelling studies of the synthesized copolymers showed a high water content in the swollen state. Biocompatibility was studied with the use of feeder-independent mouse ES cell line D3. Cells grown either on the surface or inside synthesized polymer slabs suggest that the tested slabs are not toxic. The ability of ES cells to proliferate was only partially limited in PHEMA slabs crosslinked with EDMA compared with standard culture conditions. When cultured for a limited period of time, ES cells retained their undifferentiated state independently of properties of the hydrogel slabs, presence or absence of surface charges, type of crosslinking agent and matrix (PHEMA or PVP). Notably, prolonged culture in superporous hydrogel slabs initiated ES cell differentiation. Compared with unmodified PHEMA, the number of proliferating ES cells was still lower in the presence of cationic polymers.

Animals↗
PubMed1990

Adenylate cyclase and protein kinase C mediate opposite actions on endothelial junctions.

To determine whether the endothelial paracellular pathway is regulated, the effect of intracellular messengers on the transendothelial flux of inert radiolabeled molecules of diverse molecular size was examined in bovine aortic endothelial cells grown on collagen-coated filters. The endothelial monolayers showed a modest electrical resistance (21 +/- 10 delta.cm2; m +/- SD) and restricted the passage to 14C-sucrose, 3H-inulin, 14C-dextran (70 kDa), and 125I-polyvinyl pyrrolidone (125I-PVP, 360 kDa) according to their molecular mass. 8-Bromoadenosine 3'-5' cyclic monophosphate (8-Br-cAMP) reduced by more than 30% the permeability coefficients of 14C-sucrose and 3H-inulin but had no effect on the permeability of 125I-PVP. The permeabilities of 14C-sucrose and of 14C-inulin were strikingly increased by activating protein kinase C (PKC) by phorbol 12-myristate-13-acetate or sn-1,2-dioctanoly-glycerol whereas the latter compound had no effect on the permeability of 125I-PVP. In addition, the permeability of 14C-sucrose was unchanged by a phorbol ester that does not activate PKC. Increasing intracellular calcium with ionomycin had no effect on the permeability of 14C-sucrose. None of these maneuvers significantly affected the protein content of the endothelial monolayers. The results indicate that 8-Br-cAMP and PKC activators modulate a pathway across the endothelial monolayer that excludes 125I-PVP (360 kDa) but readily accepts 14C-sucrose and 3H-inulin, suggesting that this pathway is the paracellular pathway. Hence, low molecular weight molecules such as sucrose and inulin can be used to probe the behavior of the paracellular pathway of endothelial monolayers grown in vitro. The results also indicate that the paracellular pathway in endothelium is regulated and suggest that endothelial junctions can be closed by simulating adenylate cyclase and opened by stimulating protein kinase C.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2002

Enhancements in gene expression by the choice of plasmid DNA formulations containing neutral polymeric excipients.

Formulations containing maltodextrin (2% w/v) were identified to facilitate intramuscular (im) delivery of plasmid DNA in mice using the reporter genes luciferase and chloramphenicol acetyltransferase (CAT) and the therapeutic gene of erythropoietin (EPO) as monitors of transfection efficiency. Even though considerable variability in gene expression was observed in animals, a 5-8-fold enhancement of reporter gene expression was observed with this excipient compared with saline formulations of DNA. In a therapeutically significant experiment, a single im injection of an EPO plasmid formulation containing 2% (w/v) maltodextrin resulted in a significant and prolonged elevation of the hematocrit levels of mice compared with control DNA in saline. Biophysical studies with Fourier transform infrared (FTIR) spectroscopy, isothermal titration, and differential scanning calorimetry (DSC) suggested a weak interaction between DNA and maltodextrin as well as a thermal stabilizing effect on the DNA. These in vivo and biophysical results with maltodextrin are comparable to those reported previously with other nonionic polymers, such as poly(vinyl pyrrolidone) and poloxamers, and indicate that maltodextrin is an additional nonionic excipient that displays the property of gene expression enhancement.

Animals↗
PubMed2003

Structure-activity relationship for chemical skin permeation enhancers: probing the chemical microenvironment of the site of action.

Studies were previously conducted in our laboratory on the influence of n-alkanols, 1-alkyl-2-pyrrolidones, N,N-dimethlyalkanamides, and 1,2-alkanediols as skin permeation enhancers on the transport of a model permeant, corticosterone (CS). The experiments were conducted with hairless mouse skin (HMS) in a side-by-side, two-chamber diffusion cell, with enhancer present in an aqueous buffer in both chambers. The purpose of the present study was to extend these studies and investigate in greater detail the hypothesis that a suitable semipolar organic phase may mimic the microenvironment of the site of enhancer action, and that the enhancer partitioning tendency into this organic phase may be used to predict the enhancer potency. CS flux enhancement along the lipoidal pathway of HMS stratum corneum was determined with the 1-alkyl-2-azacycloheptanones, 1-alkyl-2-piperidinones, 1,2-dihydroxypropyl decanoate, 1,2-dihydroxypropyl octanoate, n-alkyl-beta-D-glucopyranosides, 2-(1-alkyl)-2-methyl-1,3-dioxolanes, 1,2,3-nonanetriol, and trans-hydroxyproline-N-decanamide-C-ethylamide as enhancers. Enhancement factors (E values) were calculated from the permeability coefficient and solubility data over a range of E values. Comparisons of the enhancer potencies for all studied homologous series and the carbon number of the n-alkyl group revealed a nearly semilogarithmic linear relationship with a slope of approximately 0.55, which is consistent with the hydrophobic effect. Moreover, comparisons of the enhancer potencies of all the enhancers with the n-hexanol-phosphate buffered saline (PBS), n-octanol-PBS, n-decanol-PBS, and n-hexane-PBS partition coefficients showed very good correlations for the n-alkanol solvents but not for n-hexane. This result supports the interpretation that the enhancer potency is directly related to the ability of the enhancer molecule to translocate to a site of action via its free energy of transfer from the bulk aqueous phase to a semipolar microenvironment in the stratum corneum lipid lamella that is well mimicked by water-saturated n-alkanols.

Adjuvants, Pharmaceutic↗
PubMed2003

Biological, pharmaceutical, and analytical considerations with respect to the transport media used in the absorption screening system, Caco-2.

During the evaluation and selection of drug candidates, the Caco-2 cell culture system is commonly used for the determination of intestinal transport characteristics and to anticipate permeability limited drug absorption. Although classic HBSS-like buffered salt solutions are commonly used to perform Caco-2 transport experiments, different shortcomings (e.g., adsorption and low solubility) have been associated with the use of plain aqueous buffers. As transport experiments performed with unoptimized conditions may compromize the value of the Caco-2 model as a permeation screening tool, many efforts have been made to optimize the experimental conditions of Caco-2 transport assays. In this minireview, the hurdles associated with the use of saline aqueous buffers in Caco-2 transport experiments are summarized and the different options, which have been proposed to overcome these issues, are reviewed and discussed. Biologically, pharmaceutically, as well as analytically relevant media affecting the outcome of the transport experiments are described. Unfortunately, up to now, no systematic studies comparing the different experimental conditions have been performed, jeopardizing the possibility to define a (single) optimal solution to overcome the different issues associated with the use of saline aqueous buffers. Based on the reported options it can be proposed to use DMSO (<or=1%) in standard screening procedures for the ranking of compounds based on their apical to basolateral transport. If compounds are not soluble in DMSO 1%, dimethylacetamide (3%) or N-1-methyl-pyrrolidone (2.5%) are good alternatives. However, these options do not imitate the in vivo situation. If one wants to take into account the physiological relevance of the media, the use of a biologically relevant apical medium (e.g., FASSIF) in combination with an analytically friendly, sink condition creating basolateral solvent (e.g., containing a micelle forming agent) can be suggested.

Absorption↗
PubMed2003

Enhancement of dehydroepiandrosterone solubility and bioavailability by ternary complexation with alpha-cyclodextrin and glycine.

In the present work we investigated the possibility of improving dehydroepiandrosterone (DHEA) solubility and bioavailability by high-energy cogrinding with alpha-cyclodextrin (alpha-Cd) in the presence or absence of different auxiliary substances (glycine, biomaltodextrin, poly(vinyl pyrrolidone), poly(ethylene glycol) 400). In all cases, ternary products exhibited higher drug solubilizing properties than the binary DHEA-alpha-Cd coground system. Glycine was the most effective component. The best combinations, corresponding to 1:1:2 and 1:2:3 drug-alpha-Cd-glycine molar ratios, were characterized by differential scanning calorimetry and X-ray powder diffractometry and evaluated for dissolution rate. The presence of glycine favored destruction of DHEA crystalline structure during cogrinding, as evidenced by the strong reduction in both time and vibration frequency of milling necessary to obtain total drug amorphization. Both ternary products showed better dissolution properties than the drug alone, affording, respectively, a 40 and 60% increase of dissolution efficiency. The 1:2:3 coground product was then selected for in vivo bioavailability studies in women suffering from adrenocortical insufficiency. DHEA and DHEA sulfate blood levels were significantly higher (p < 0.001) after oral administration of the coground product than after oral administration of untreated drug, with a 100% increase in the area under the curve (AUC) of concentration versus time. Moreover, the time to reach maximum concentration (t(max)) decreased from 2.2 with the untreated drug to 0.5 h with the coground product, and the mean permanence time of DHEA within physiological levels was four times longer for the coground product compared with the untreated drug. These results indicate that the developed product is particularly suitable for oral DHEA formulations in hormone replacement therapies.

Adrenal Cortex Diseases↗
PubMed2004

Rapid dissolution of high-potency danazol particles produced by evaporative precipitation into aqueous solution.

High-potency danazol particles with high dissolution rates were produced by evaporative precipitation into aqueous solution (EPAS). Aqueous suspensions formed by EPAS were centrifuged to remove the nonadsorbed surfactant. The resulting surfactant-coated drug particles had extremely high drug-to-surfactant ratios greater than 5, corresponding to potencies (wt drug/wt drug + wt surfactant) as high as 93%. The mechanism of the high dissolution rates was characterized as a function of surfactant adsorption, particle size and surface area, drug crystallinity, and the contact angle for water on the drug surface. For danazol stabilized by polyvinyl pyrrolidone (PVP) alone or with sodium lauryl sulfate (SLS), small particle diameter and high surface area led to high dissolution rates with approximately 90% drug dissolved in 2 min. The crystallinity of the danazol was typically 80%. The properties of the particles and the dissolution rates were mostly unchanged under a 2-week thermal cycling stress test.

Chemical Precipitation↗
PubMed2004

Mechanistic study of chemical skin permeation enhancers with different polar and lipophilic functional groups.

In a previous study, the enhancement effects on the transport of a steroidal permeant along the hairless mouse skin (HMS) stratum corneum (SC) lipoidal pathway were investigated for two homologous series of chemical enhancers: the 1-alkyl-2-pyrrolidones and the 1-alkyl-2-azacycloheptanones. The objective of the present study was to extend this investigation to a broader range of enhancers in order that generalizations with regard to the mechanistic aspects of enhancer function might be established. Specific questions to be addressed included: (a) what is the nature of the microenvironment of the enhancer site of action? (b) what is the extent of the equilibrium uptake of the enhancer from its E = 10 aqueous enhancer solution (the aqueous concentration for which the enhancer induces a tenfold transport enhancement) into the HMS SC intercellular lipid "phase"? and (c) are the microenvironment of the enhancer site of action and that for the equilibrium enhancer uptake at E = 10 relatively independent of the molecular characteristics of the enhancers (as suggested by the earlier study)? Enhancers selected for this study included: a wide range of polar head group size and polarity; n-alkyl group chain lengths from C(4) to C(12); and enhancers in which a double bond is substituted for a single bond in the hydrocarbon chain (3-alkenols) from C(5) to C(9). In addition to the main study, an ancillary set of experiments were to be conducted on the partitioning of a surrogate permeant (estradiol) into the intercellular lipid "phase" under E = 10 isoenhancement conditions to assess the extent to which the permeant partition coefficient may contribute to the permeation enhancement. The following were the principal findings of this research. First, there was very good correlation between the E = 10 isoenhancement aqueous enhancer concentrations and K(octanol/water) for all the studied enhancers. Second, the partitioning of the enhancer from the E = 10 aqueous enhancer solution into the HMS SC intercellular lipid "phase" was found to be relatively independent of the molecular characteristics for all studied enhancers, and the partition coefficients also correlated well with K(octanol/water). These results may have the following meanings: both the microenvironment of the enhancer site of action and the SC intercellular lipid "phase" involved in the enhancer partitioning experiments are well mimicked by liquid n-octanol, and the "intrinsic" potencies (as assessed by the equilibrium enhancer concentration in the microenvironment at the site of action) of the enhancers are relatively independent of the molecular characteristics of the studied enhancers. Finally, the estradiol partitioning experiments suggest the permeant partitioning into the HMS SC intercellular lipid "phase" is enhanced around five- to seven-fold when permeation is enhanced ten-fold for most of the studied enhancers; therefore, the enhancement of the permeant partition coefficient rather than the permeant diffusion coefficient seems to be more important in permeation enhancement of the SC barrier lipoidal pathway.

Animals↗
PubMed2005

Effects of acidic N + 1 residues on asparagine deamidation rates in solution and in the solid state.

The deamidation kinetics of four model peptides (AcGQNGG, AcGQNDG, AcGQNEG, and AcGQNQG) were studied in solution (70 degrees C, pH 5-10) and in lyophilized solids [70 degrees C, 50% relative humidity, "effective pH" ('pH') 5-10] containing polyvinyl pyrrolidone. AcGQNGG, AcGQNEG, and AcGQNQG degraded exclusively through Asn deamidation, whereas AcGQNDG also displayed Asp isomerization, and Asp-Gly peptide bond cleavage. The pH/'pH'-rate profiles were consistent with a shift in the rate-determining step of Asn deamidation from carbonyl addition to expulsion of ammonia with increasing pH. In solution, AcGQNGG deamidated up to 38-fold faster than the other peptides, indicating the importance of steric effects of the N + 1 residue. AcGQNGG and AcGQNQG had up to 60 times slower rates of deamidation in the solid state than in solution. In contrast, the deamidation rates of AcGQNEG and AcGQNDG in the solid state were similar to those in solution. N + 1 Glu or Asp residue may enhance local hydration, so that the deamidation of Asn in the solid formulations actually proceeds in a solution-like environment.

Amides↗
PubMed2005

Deamidation of model beta-turn cyclic peptides in the solid state.

To investigate the importance of secondary structure on peptide deamidation in the solid state, two cyclic beta-turn peptides and their linear analogs were used as models of Asn residues in structured and unstructured domains, and incorporated into poly(vinyl pyrrolidone) (PVP)-based lyophilized solids. The secondary structure of the model peptides was determined in solution and the solid state using a combination of nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD), and Fourier transform infrared (FTIR) spectroscopy. The model beta-turn cyclic peptides were found to be type II beta-turns while the linear analogs were determined to be predominantly unstructured. Quantitatively, the cyclic peptides consisted of approximately 80% beta-turn while the linear analogs contained only 30%-35% beta-turn. To characterize the solid environment, T(g), and moisture content of the solid-state formulations were determined. Accelerated stability studies were conducted in the solid state at 37 degrees C using formulations lyophilized from solutions at pH 8.8 (0.1 M borate buffer). The effect of matrix mobility on solid-state deamidation was investigated by altering the moisture content through variation of relative humidity or the addition of a plasticizer. Cyclic peptides degraded 1.2-8 times slower than the linear analogs under all of the conditions studied. The observed rate constants, however, for all of the peptides decreased dramatically (four orders of magnitude) in the glassy solids. This suggests the greater importance of matrix mobility in solid-state degradation. Molecular dynamics (MD) simulations were also performed to explore the low energy, preferred state of the peptides, and determine the structure around the beta-turn.

Amides↗
PubMed2006

Molecular mobility of nifedipine-PVP and phenobarbital-PVP solid dispersions as measured by 13C-NMR spin-lattice relaxation time.

Amorphous nifedipine-PVP and phenobarbital-PVP solid dispersions with various drug contents were prepared by melting and subsequent rapid cooling of mixtures of PVP and nifedipine, or phenobarbital. Chemical shifts and spin-lattice relaxation times (T(1)) of PVP, nifedipine, and phenobarbital carbons were determined by (13)C-CP/MAS NMR to elucidate drug-PVP interactions and the localized molecular mobility of drug and PVP in the solid dispersions. The chemical shift of the PVP carbonyl carbon increased as the drug content increased, appearing to reach a plateau at a molar ratio of drug to PVP monomer unit of approximately 1:1, suggesting hydrogen bond interactions between the PVP carbonyl group and the drugs. T(1) of the PVP carbonyl carbon in the solid dispersions increased as the drug content increased, indicating that the mobility of the PVP carbonyl carbon was decreased by hydrogen bond interactions. T(1) of the drug carbons increased as the PVP content increased, and this increase in T(1) became less obvious when the molar ratio of PVP monomer unit to drug exceeded approximately 1:1. These results suggest that the localized motion of the PVP pyrrolidone ring and the drug molecules is reduced by hydrogen bond interactions. Decreases in localized mobility appear to be one of the factors that stabilize the amorphous state of drugs.

Carbon Isotopes↗
PubMed2006

Manipulation of beclomethasone-hydrofluoroalkane interactions using biocompatible macromolecules.

The aim of this work was to physically stabilise beclomethasone dipropionate (BDP) microparticles within a hydrofluoroalkane (HFA) propellant using biocompatible polymers in order to allow the efficient delivery of the steroid to the airways from a pressurised metered dose inhaler (pMDI). BDP microparticles were coated with a number of different "amphiphilic" macromolecular excipients by spray-drying an aqueous BDP suspension in which the excipients were dissolved. The physical stability of the coated BDP microparticles was assessed both indirectly using a twin-stage impinger (TSI) and directly using "in-situ" laser diffraction particle size analysis in a range of nonpolar solvents. The solubility of the formulation excipients within a number of the nonpolar vehicles was determined using an internally manufactured filtration rig and the influence of zeta potential within the microparticle suspensions measured in a series surrogate nonpolar systems. The size of the pure BDP microparticles increased significantly (p < 0.05, ANOVA) from 3.13 +/- 0.15 microm to 9.86 +/- 0.50 microm upon suspension within a nonpolar HFA solvent. However, the addition of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) to the BDP microparticles dramatically reduce this aggregation leading to the production of physically stable suspensions with excellent aerosolisation properties (Stage 2 deposition >40% in the twin-stage impinger). It is postulated that the enhanced physical stability observed when PVA and PVP are coated onto BDP microparticles is partially as a result of steric stabilisation in HFA solvents. However, the large zeta potential associated with the nonpolar microparticle suspensions suggest that charge stabilisation may also influence the physical stability within these systems.

Aerosol Propellants↗
PubMed1977

Bioavailability and activity of topical corticosteroids from a novel drug delivery system, the aerosol quick-break foam.

Experiments were conducted to: (a) compare the bioavailability of betamethasone benzoate in a quick-break aerosol foam and semisolid dosage forms, (b) compare the activity of betamethasone benzoate, betamethasone valerate, clobetasol propionate, triamcinolone acetonide, desonide, flumethasoid reservoir formation in skin, and (d) assess the effect of a natural moisturizer. Efficacy was determined by a graded response 6-hr occluded vasoconstriction test with subsequent reocclusion for reservoir demonstration. Moisturizer effect was assessed by a nonoccluded vasoconstriction test using "plain" and sodium 2-pyrrolidone-5-carboxylate-containing concentrates on arms pretreated with water or moisturizer. The activities of betamethasone benzoate concentrate, collapsed foam, ointment, and gel were similar and significantly better than the activity of the cream. Clobetasol propionate was significantly better than the other medicated concentrates, which were equivalent. Steroid-induced blanching decreased in the presence of a moisturizer.

Administration, Topical↗
PubMed1979

Structure of polyvinylpyrrolidone-iodine (povidone-iodine).

Hydrogen triiodide adducts were prepared from N,N-dimethylacetamide, N-alkylpyrrolidone derivatives, and polyvinylpyrrolidone, and their structures were investigated by IR spectra and X-ray structure analyses and compared with the structure of povidone-iodine USP. The results suggest that the iodine in povidone-iodine USP is complexed by the polymer such that a proton is fixed via a short hydrogen bond between two carbonyl groups of two pyrrolidone rings and that a triiodide anion is bound ionically to this cation.

Chemical Phenomena↗
PubMed1985

Pharmacokinetics of morphine and its surrogates. VII: High-performance liquid chromatographic analyses and pharmacokinetics of methadone and its derived metabolites in dogs.

Reversed-phase HPLC assays with on-column UV detection and post-column fluorescent detection of ion pair-extracted material were developed and used for the quantitative assay of methadone, its presumed metabolites, and acid- and alkali-hydrolyzable conjugates of these metabolites in biological fluids with assay sensitivities of 10-20 ng/mL. Plasma, urine, and bile were monitored in dogs after intravenous bolus administration of 0.8, 1.0, 2.0, and 2.2 mg/kg methadone hydrochloride. Plasma-time data showed two sequential half-lives of 8.3 +/- 3.4 (SEM) and 128 +/- 37 min, with apparent dose-independent pharmacokinetics in the studied dose range. Total body clearances were 899 +/- 103 (SEM) mL/min. Renal clearances (6-82 mL/min) of methadone were highly variable within and among studies but showed no significant variation with urinary pH or flow rate. The percentages of the dose excreted in the urine as methadone and (+)-2-ethyl-1,5-dimethyl-3,3-diphenylpyrroline (2) were 3.6 +/- 0.5% (SEM) and 4.1 +/- 0.4% (SEM), respectively, but there were no significant concentrations of 2 in plasma. The presumed metabolites 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline (3), 1,5-dimethyl-3,3-diphenyl-2-pyrrolidone (4), (-)-alpha-N-normethadol (7), 4-dimethylamino-2,2-diphenylvaleric acid (8), p-hydroxymethadone (9), and (-)-alpha-methadol (10) were not observed in the plasma of dogs given methadone. Quantities of presumed metabolites 3, 4, 7, 8, 9, and 10 were negligible in urine (less than 0.03% of dose). No acid-hydrolyzable conjugates, or generators on acidification, of 3, 4, 7, 8, or 10 were detectable in urine. No alkali-hydrolyzable conjugates, or generators on alkalinization, of 3, 4, 8, or 10 were detectable in urine. There was no significant biliary secretion of unchanged methadone; 2 in bile amounted to only 2% of the dose. In bile and urine, 50% and 17-27%, respectively, of the radiolabeled dose was not extractable into hexane. In a non-bile-cannulated dog, 35% of the total radiolabeled intravenous dose was present in the feces. As much as 88% of an intravenous radiolabeled dose could be accounted for, even though only small amount of methadone was disposed through the metabolic routes claimed in the literature. The intravenous administration of 2 resulted in two sequential half-lives of 3 and 270 min and no apparent pharmacokinetic dose dependency. Amounts of 2 excreted unchanged in urine and bile were 23% and 5-16% of the dose, respectively. Renal and total body clearances were 170 and 1150 mL/min.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Large-scale production of liposomes containing monomeric zinc phthalocyanine by controlled dilution of organic solvents.

This work describes the development of an organic solvent dilution method suitable for the large scale manufacturing of small unilamellar liposomes containing the water-insoluble photosensitizer zinc phthalocyanine in the monomeric state. N-Methyl pyrrolidone (NMP)/tert-butyl alcohol was selected as water miscible organic phase in which the phospholipids 1-palmitoyl, 2-oleoylphosphatidylcholine (POPC), and 1,2-dioeloylphosphatidylserine (OOPS) and the dye were dissolved. This organic phase was mixed with an excess of a water phase using a dynamic mixing device, yielding reproducibly unilamellar liposomes with a mean size of 50-150 nm as measured with quasielastic light scattering. After concentration, the organic solvents were efficiently removed by cross-flow filtration. The liposomes were then sterile filtered and freeze-dried. A method to measure the aggregation state of the dye in the liposomes was developed. A stable lyophilized formulation containing monomeric liposomal ZnPc could be obtained by using a solution of ZnPc in NMP (2 mg/mL) and ZnPc/phospholipid (1:100 w/w ratio) and performing concentration and dialysis at 4 degrees C and lyophilization in presence of a mixture of lactose and phospholipid (5:1 w/w ratio).

Chromatography, Gas↗
PubMed1995

Effect of various enhancers on transdermal penetration of indomethacin and urea, and relationship between penetration parameters and enhancement factors.

The enhancing capacity of various chemicals, which are widely recognized as enhancers, for the transdermal penetration into full-thickness rat skin of a model lipophilic drug [indomethacin (IND)] and a hydrophilic permeant (urea) was estimated by an in vitro technique. In addition, the fluidity of the stratum corneum lipids, the partitioning of IND into skin, the lipid (ceramides) extraction from the stratum corneum by enhancers, and the IND solubility in enhancer vehicle were measured and related to the enhancing capacity. In vitro permeation experiments with hairless rat skin unequivocally revealed that the enhancers varied in abilities to enhance the fluxes of both agents. Laurocapram, isopropylmyristate (IPM), sodium oleate, and cineol increased fluxes of both agents to a great extent, but N-methyl-2-pyrrolidone (NMP), N,N-diethyl-m-tolamide (DEET), and oleyl oleate were less effective acclerants. Many enhancers increased the fluidity of the lipids [with a threshold of approximately 0.6-0.8 ns at 37 degrees C in the rotational correlation time (tau c)], the skin partitioning of IND, the extraction of ceramides from the cornified cells, and the thermodynamic activity of IND in vehicle (calculated from the solubility) to varying extents. A good correlation was observed between the increase in the fluidity of stratum corneum lipids and the partitioning of IND into skin, between the increase in the fluidity and the flux or the decrease in lag time for IND, between the removal of ceramides and the skin partitioning of IND, and between the removal of ceramides and the flux of urea (p < 0.05 in all cases).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗