<prompt> Entacapone may be useful in patients being treated with levodopa-carbidopa combination because it :Activates COMTDecreases formation of 3OMDInhibits monoamine oxidase type BInhibits dopamine uptake  <response>: Levodopa is converted to dopamine by dopa decarboxylase that cannot cross the blood-brain barrier.Carbidopa is an inhibitor of dopa decarboxylase in the periphery. It therefore increases the amount of l-dopa that reaches the brain due to inhibition of peripheral metabolism to dopamine.Due to inhibition of l-dopa metabolism by dopa decarboxylase, an alternative pathway of metabolism by catechol-O-methyl transferase COMT is activated.COMT metabolizes l-dopa to 3-O-methyldopa 3-OMD that can complete with l-dopa for entry in the brain.Entacapone and tolcapone is useful in Parkinsonism by inhibiting COMT. 