How is it determined whether or not a compound is a P-gp substrate?
A compound is considered to be a P-gp substrate if the calculated efflux ratio, PB→A / PA→B , is >2. Our procedure and efflux ratio calculation are outlined in the FDA’s Draft Guidance for Industry, Drug Interaction Studies—Study Design, Data Analysis, and Implications for Dosing and Labeling, 2006.
