Search results for "penetration"
showing 10 items of 168 documents
Skin-PAMPA: a new method for fast prediction of skin penetration.
2011
The goal of this study was to develop a quick, reliable, and cost-effective permeability model for predicting transdermal penetration of compounds. The Parallel Artificial Membrane Permeability Assay (PAMPA) was chosen for this purpose, as it already has been successfully used for estimating passive gastrointestinal absorption and blood-brain barrier permeability. To match the permeability of the rate-limiting barrier in human skin, synthetic certramides, which are analogs of the ceramides present in the stratum corneum, were selected for the skin-PAMPA model. The final skin-PAMPA membrane lipid mixture (certramide, free fatty acid, and cholesterol) was selected and optimized based on data …
Ocular Penetration of Topically Applied Norfloxacin 0.3% in the Rabbits and in Humans
1992
The kinetics of topically applied norfloxacin 0.3 percent were studied in rabbit and man. All measurements were performed by high-pressure liquid chromatography. Norfloxacin concentrations were investigated five to 120 minutes in rabbit ocular tissues after instillation of a single drop. In normal eyes, after 30 minutes, mean +/- SEM levels were 14.3 +/- 3.7 micrograms/g in cornea, 3.3 +/- 0.7 micrograms/g in conjunctiva, 0.2 +/- 0.1 microgram/g in aqueous humor. After removal of the corneal epithelium concentrations were as follows: 84.2 +/- 15.8 micrograms/g, 7.3 +/- 2.3 micrograms/g, 8.6 +/- 1.9 micrograms/g respectively. Penetration in posterior ocular tissues were rather poor. In human…
Augmented glucose-6-phosphate dehydrogenase activity and normal penetration and metabolism of dehydroepiandrosterone in mononuclear leukocytes in pso…
1986
The aim of the study was to determine a biochemical basis for the augmented oxidative metabolism found in mononuclear leukocytes (MNL) of patients with active psoriasis. Dehydroepiandrosterone (DHEA) is known to inhibit glucose-6-phosphate dehydrogenase (G-6-PDH). We determined the activity of G-6-PDH as well as the penetration and metabolism of DHEA - diminished plasma concentrations of which have been found in psoriatics previously - in 16 patients with active psoriasis and 16 controls. MNL in patients with psoriasis possessed 52% more (p less than 0.05) G-6-PDH activity, based on cell number, and 34% more (p less than 0.05) activity, based on soluble protein. No difference in DHEA penetr…
In Vitro Percutaneous Penetration of Acyclovir from Solvent Systems and Carbopol 971-P Hydrogels: Influence of Propylene Glycol
2005
The mechanism underlying propylene glycol (PG) effects on acyclovir (ACV) penetration through human epidermis were studied. Solvent systems and Carbopol gels containing increasing percentage of PG (from 0% to 70%, w/w) were used. Viscosity studies of both vehicles were carried out to characterise the influence of rheological behaviour. In solvent systems skin permeation values of ACV increase as the concentration of PG increase yielding a maximum enhancement ratio (ER = 10) for 70% PG. The release rate of ACV from gels was determined. Higuchi's model was used to estimate the apparent diffusion coefficient of the drug. These values show a decrease as the content of PG in the vehicle increase…
Enhancement of nortriptyline penetration through human epidermis: influence of chemical enhancers and iontophoresis.
2008
Abstract Different known percutaneous chemical enhancers and iontophoresis have been tested in-vitro to study their ability to increase transdermal absorption of nortriptyline hydrochloride (20 mg mL−1). The chemicals 1-dodecanol, Span 20, Azone, (R)-(+)-limonene or isopropyl myristate were used as an overnight pretreatment at 5% (w/w) in ethanol. Furthermore, isopropyl myristate (20%, w/w) and propylene glycol (15%, w/w) were tested in the same vehicle. Iontophoresis was applied directly to the nortriptyline hydrochloride donor solution for three different concentrations (20, 2 and 0.5 mgmL−1). The chemical enhancers slightly increased the nortriptyline transdermal flux but iontophoresis w…
Enhanced In Situ Availability of Aphanizomenon Flos-Aquae Constituents Entrapped in Buccal Films for the Treatment of Oxidative Stress-Related Oral D…
2019
In recent years, the key role of oxidative stress in pathogenesis of oral diseases has been emphasized and the use of antioxidant agents has been encouraged. Aphanizomenon flos-aquae (AFA) is a unicellular blue-green alga with antioxidant and anti-inflammatory properties. The aim of this study was the formulation and characterization of mucoadhesive thin layer films loaded with AFA, finalized to the treatment of oxidative stress (OS)-related oral diseases. First, to enhance the bioavailability of AFA constituents, the raw food grade material was appropriately treated by a high frequency homogenization able to disrupt cell walls. Thus, Eudragit®
On Pathways for Small Molecules Into and Out of Human Hair Fibers
1996
This paper represents an experimental approach of histology of the human hair fiber in dyeing and diffusion phenomena and its contribution to the interpretation of hair analysis results for drug abuse. Rhodamine B was applied to human hair fibers from either aqueous solution or methanol/ethanol solvent. The experiments were performed on natural hair of different ethnic groups as well as on extensively bleached hair strands. The microscopical study of the pathway of diffusion of rhodamine B into the hair fibers indicated that the reagent had entered the unmodified fibers at the scale edges between the cuticle cells. At the beginning of the diffusion process intercellular diffusion was the pr…
A modelistic approach showing the importance of the stagnant aqueous layers in in vitro diffusion studies, and in vitro-in vivo correlations
1991
Abstract The present study deals with the role of the aqueous diffusion layers on the in vitro penetration of xenobiotics across artificial lipoidal membranes, and their ability to reproduce biophysical absorption models when in vivo results are to be simulated from the in vitro tests. The aqueous boundary layers which are invariably formed on artificial lipoidal membranes can be optionally preserved or disrupted, according to the type of absorption site which should be simulated, a condition which could reasonably lead to a better correspondence between in vitro and in vivo results; in practice, disruption of water layers can be easily achieved by a synthetic surfactant solution at its cri…
Depth selective Mössbauer spectroscopy: Analysis and simulation of 6.4 keV and 14.4 keV spectra obtained from rocks at Gusev Crater, Mars, and layere…
2008
[1] The miniaturized Mossbauer spectrometer (MIMOS) II Mossbauer spectrometers on the Mars Exploration Rovers (MER) simultaneously obtained 6.4 keV and 14.4 keV Mossbauer spectra from rock and soil targets. Because photons with lower energy have a shallower penetration depth, 6.4 keV spectra contain more mineralogical information about the near-surface region of a sample than do 14.4 keV spectra. The influence of surface layers of varying composition and thickness on Mossbauer spectra was investigated by Monte Carlo simulation and by measurement using a copy of the MER MIMOS II instrument and samples with one or two layers of known thicknesses. Thin sections of minerals or metallic Fe foil …
Prior Precision Modulates the Minimization of Auditory Prediction Error
2019
International audience; The predictive coding model of perception proposes that successful representation of the perceptual world depends upon canceling out the discrepancy between prediction and sensory input (i.e., prediction error). Recent studies further suggest a distinction to be made between prediction error triggered by non-predicted stimuli of different prior precision (i.e., inverse variance). However, it is not fully understood how prediction error with different precision levels is minimized in the predictive process. Here, we conducted a magnetoencephalography (MEG) experiment which orthogonally manipulated prime-probe relation (for contextual precision) and stimulus repetition…