of CYP2C9 are competitive inhibitors. (source) In competitive inhibition, when the inhibitor binds to the active site on the enzyme, it prevents binding of the substrate and vice versa. Noncompetitive inhibitors of CYP2C9 include: 6-hydroxyflavone (found in the leaves of Barleria prionitis (aka the porcupine flower) medroxyprogesterone acetate (aka MPA; a