bioassay specification pharmacokinetic assay parallel artificial membrane permeability assay PAMPA A method which determines the permeability of substances from a donor compartment, through a lipid-infused artificial membrane into an acceptor compartment. At the beginning of the test, the drug is added to the donor compartment, and the acceptor compartment is drug-free. After an incubation period the amount of drug is measured in each compartment. Mass balance allows calculation of drug that remains in the membrane. It is used as an in vitro model of passive, transcellular permeation to predict oral absorption. PAMPA is an alternative to the cell-based Caco-2 permeability assay