Figure 1: Impact of drug-transporting proteins and metabolizing enzymes on intracellular drug bioavailability (Fic, the fraction of externally added drug that is available to bind targets in the cell interior).
From: Intracellular drug bioavailability: a new predictor of system dependent drug disposition
Uptake transporters (green, e.g. OATP1B1) increase the Fic, while efflux transporters (light orange, e.g. P-gp) and metabolizing enzymes (dark orange, e.g. CYP3A4) lower the Fic. Arrows represent diffusion over the plasma membrane (passive lipoidal transmembrane diffusion or carrier-mediated diffusion).
