• Diffusion and absorption of drugs

Drug permeability is one of the most important factors to be considered for predicting oral drug bioavailability. Permeation mechanisms through biological barriers include active transport, passive diffusion, paracellular, and efflux. The body absorbs nearly 80~95% of the recorded commercial drugs through passive diffusion.

For permeability screening, the Caco-2 cell monolayer permeation method has been widely and successfully used in drug discovery and early development. With the need for reduced cost, increased predictability, and higher throughput in drug discovery, other methods are needed to assist Caco-2 assay.

• Why PAMPA?

PAMPA uses two aqueous buffer solution holes separated by an artificial membrane. The artificial membrane is composed of a lipid-oil-lipid sandwich structure in an organic diluent supported by a porous filter plate matrix. And then, the test compound diluted in the buffer is placed in the donor well. The compound enters the artificial membrane from the donor pore, entering the acceptor pore by passive diffusion. The compound's effective permeability (Pe) is utilized to determine the rate of permeation. Compared with cell-monolayer methods, the time required for the experiment is greatly reduced. Only passive diffusion is tested, and there is no metabolism, no transporter proteins, so there is no need to worry about saturation.