DPI is an irreversible inhibitor of iNOS and eNOS with IC50 values of 50 nM and 0.3 μM, respectively.{952} This inhibition is potent, irreversible, and time and temperature dependent.{952} NADPH, NADP+, and 2'5'-ADP block the inhibitory action of DPI. Similarly, FAD or FMN protect NOS from inhibition by DPI.{952}