The Pion PAMPA assay is used as an in vitro model of passive, transcellular permeability. An artificial membrane immobilized on a filter is placed between a donor and acceptor compartments. At the start of the test, a drug is introduced in the donor compartment.ince the pH of the blood is pH 7.4; there exists a pH gradient between the GIT and the plasma that can affect the transport of ionizable molecules. In an effort to simulate this pH gradient, we have chosen pH 7.4 for the acceptor compartment, and a pH range of 5.0, 6.2, and 7.4 in the donor compartment.
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