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Intestinal Absorption
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Ready-to-use assay systems for DMPK and ADMET studies

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Intestinal Absorption

A ready-to-use liposome-based kit for rapid in vitro assessment of the ability of drugs to cross the intestinal epithelium.

  • Ready-to-use 96-well microtiter plates carrying TRANSIL beads with a single lipid bilayer reconstituted from phosphatidyl choline, designed to conveniently measure membrane binding and membrane permeability.
  • Kit includes spreadsheet, facilitating manipulation of statistical parameters and calculation of final results and a prediction of the volume of distribution (Vss).
  • Designed for automated liquid handlers or manual pipetting.
  • TRANSIL beads are integrated into 96-well microtiter plates to enable easy handling.
  • One plate can be used for measuring membrane binding and membrane permeability of up to 12 compounds.
  • Only 12 minutes assay incubation time.
  • Rapid compound quantification due to immobilized plasma proteins (e.g. injection via RapidFire™).
  • Highly reproducible results and robust correlation with conventional dialysis technique.
Background and Technical Information

The half-life of a drug is a major contributor to the dosing regimen is a function of both the clearance and apparent volume of distribution (VD), each of these parameters can be predicted and combined to generate a half-life value. Drugs with short half-lives are likely to be administered more frequently than those with long half-lives. The dosing regimen is also intrinsically linked to other factors such as: the drug’s pharmacodynamics and the difference between systemic concentrations associated with side effects versus those minimally required for efficacy. However, these latter attributes are much more difficult to predict from in vitro or animal data and will be different for each therapeutic target. Thus, a great deal of focus has been placed on the prediction of human half-life. While methods using allometric scaling or correlative methods exist to predict a half-life, greater success is attained if the two major components of half-life, clearance and volume of distribution, are predicted separately and combined to generate a half-life prediction.

VD represents a complex combination of multiple chemical and biochemical phenomena. It is a measure of the relative partitioning of a drug between plasma (the central compartment) and the tissues. Thus, the VD term considers all of the tissues as a single homogeneous compartment.

Compounds that are equally bound to plasma proteins may yield a different VD, since the compound with the greater tissue binding will yield the larger VD. Conversely, compounds with equal tissue binding may differ in VD, with compounds that have the greater plasma protein binding yielding the smaller volume of distribution. Drug partitioning into tissues is a function of the sum of binding interactions with tissue components versus binding to plasma proteins, provided that the drug can readily penetrate the tissues. It should be noted that, realistically, binding to the various tissues is a function of the composition of each tissue, which dictates the binding affinities and capacities for various drugs. However, while it is simple to measure plasma protein binding using human plasma, measurement of tissue binding in humans is not practical.

The TRANSIL Intestinal Absorption Kit is not only a screening tool to predict intestinal permeability coefficients, but also predicts compounds’ tissue binding. As drug-membrane interactions are key to both the process of membrane permeability and binding to and permeating into the cell membranes of tissues the TRANSIL assay kit based on immobilized natural phosphaticylcholine membrane vesicles is an ideal tool to predict these pharmacokinetic parameters early in drug discovery.

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