Derudover methyleres stoffet af COMT til 3- O- methyltolcapon og metaboliseres af cytochrom P450 3A4 og P450 2A6 til en primær alkohol (hydroxylering af methylgruppen), som derefter oxideres til carboxylsyren.
In addition, the compound is methylated by COMT to 3-O-methyl-tolcapone and metabolised by cytochromes P450 3A4 and P450 2A6 to a primary alcohol (hydroxylation of the methyl group), which is subsequently oxidised to the carboxylic acid.