Permeability data

The experimental procedure and method of treatment of compression-permeability data have been explained by Grace [Chem. Eng. Prog., 49, 303, 427 (1953)], who showed that the values of a measured in such a cell and in a pressure filter were the same, and by Tiller [Filtr Sep., 12, 386 (1975)]. 

Table 5.11 Permeability data for various polymers values for P X 10 cm- s mm cm cmHg...

Once the 2% DOPC/dodecane permeability data have been corrected for pH and UWL effects, the resulting intrinsic permeabilities Pq should be linearly related... 

Walter,E. Janich, S. Roessler, B.J. Hilfinger,J.M. Amidon, G. L., HT29-MTX/Caco-2 cocultures as an in vitro model for the intestinal epithelium In vitro-in vivo correlation with permeability data from rats and humans, J. Pharm. Sci. 85, 1070-1076 (1996). 

It is obvious from Equation 14.14 that the most important parameter determining the volumetric air flow rate <2W is the intrinsic permeability K of soil. At this point it is important to stress the difference between water permeability (or hydraulic conductivity) k , air permeability ka, and intrinsic permeability K. In most cases, when permeability data are provided for a type of soil or geological formation, these data are based on hydraulic conductivity measurements and describe how easily the water can flow through this formation. However, the flow characteristic of a fluid depends greatly on its properties, e.g., density p and viscosity p. Equation 14.16 describes the relationship between permeability coefficient k and fluid properties p and p ... 

Figure 5 Correlation of the fraction of dose absorbed with rat permeability. The rat permeability data were determined using the rat perfusion model. Considering the difference between the human permeability and the rat permeability, a scale factor was used to calculate the absorption number in Eq. (8). (Ref. 34 with kind permission from Plenum Publishing Corporation, New York.)...

When comparing different experimental sources of Caco-2 permeability data, quantitative comparison is almost impossible, due to intervariations of experimental procedures between laboratories, although standard protocols and reference molecules are often used. 

Figure 1. Plot of permeability data using Equation...

Table 4. Permeability data for selected capsules with glucose as a permeate... 

Table II. Permeability data for COTS metallic glass materials compared to Pd...

Johnson BM, Charman WN, Porter CJH (2003) Application of compartmental modelling to an examination of in vitro intestinal permeability data Assessing the impact of tissue uptake, P-glycoprotein, and CYP3A. Drug Metab Dispos 31 1151-1160. 

For some compounds in the Wilschut database more than one permeability coefficient was gathered from literature. In some cases, the differences in kp were greater than one log unit underlining the interlaboratory variations of such measurements. For the development of a new QSPR model one may now either choose one representative data point for each molecule or combine the multiple data points in a reasonable way. In some cases authors even employed all the available data for a single compound. Apart from the permeability data, the data on the partition coefficient and even on the molecular weight may vary from one report to another. Differences in the partition coefficient are easily explained Some collections list experimentally determined values which depend on the experimental procedure employed... 

A linear fit of Eq. 12 to experimental permeability data for cell membranes gave a good correlation. Lieb and Stein determined also the value of c for several different cell membranes and found c to be equal or greater than one in all cases, which suggests that diffusion in cell membranes resembles diffusion in synthetic polymers. 

To determine the molecular properties influencing the diffusion process they investigated the relationship between experimental stratum corneum-water partition coefficients and permeability data for 45 compounds. Rearrangement of the logarithmic form of Eq. 4 led to... 

Scheuplein RJ (1966) Analysis of permeability data for the case of parallel diffusion pathways. Biophys J 6 1-17. 

PK-Map and PK-Sim (Bayer Technology Services, Wuppertal, Germany), that are based on the models described by Willman et al. [54], In these software packages, the intestinal permeability coefficient can be calculated using a compound s lipophilicity and molecular weight [52,54] and hence, no experimental permeability data is needed. Different to the model described by Willman et al. [54], the commercial prediction tools model the dissolution rate taking the particle size distribution of the solid particles into account (www.pk-sim.com). 

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