Figure 2.

Direct and indirect modification of drug efficacy by gut microbiota. (A) Gut microbiota directly binds to drugs such as L-dopa. (B) Gut microbiota can inactivate, activate or change the potency and bioavailability of drugs via direct enzymatic metabolism. (C) Drugs modulate the composition and metabolism of gut microbiota to achieve efficacy. (D) Drugs modulate the spatial distribution of gut microbiota to achieve efficacy. (E) Gut microbiota synthesizes compounds with the ability to modulate and compete for drug transporters. Please see article text for the details on interactions and effects.