<prompt> Entacapone may be useful in patients being treated with levodopacarbidopa combination because it:Activates COMTDecreases formation of 3-OMDInhibits monoamine oxidase type BInhibits dopamine uptake  <response>: Ref: KDT 6e p421 Levo-dopa is conveed to dopamine by dopa decarboxylase that cannot cross blood brain barrier. Carbidopa is an inhibitor of dopa decarboxylase in the periphery. It therefore increases the amount of 1-dopa that reaches the brain due to inhibition of peripheral metabolism to dopamine. Due to inhibition of 1-dopa metabolism by dopa decarboxylase, an alternative pathway of metabolism by catechol-o-methyl transferase COMT is activated.COMT metabolizes 1-dopa to 3-o-methyl dopa 3-OMD that can complete with 1-dopa for entry in the brain. Entacapone and tolcapone is useful in Parkinsonism by inhibiting COMT. 