Difference in erythrocyte catechol-O-methyltransferase activity between Orientals and Caucasians: difference in levodopa tolerance.

The same bimodal distribution of erythrocyte catechol-O-methyltransferase (RBC-COMT) was found in normal Caucasians and Orientals, but the frequency distribution of high RBC-COMT activity of the Orientals was significantly greater than that of the Caucasians. There was no difference in RBC-COMT frequency distribution between Oriental ethnic groups studied (i.e., Chinese and Filipinos). Since Caucasians with Parkinson's disease who had high RBC-COMT activity appeared to have more adverse effects from levodopa (L-dopa) than had those with low RBC-COMT activity, L-dopa doses and adverse responses in Filipinos with parkinsonism were compared to those of Caucasians with parkinsonism. The Filipinos were prescribed substantially lower doses than were the Caucasian patients, and more Filipinos than Caucasians developed dyskinesia at comparable doses of L-dopa. The possible association of the clinical differences in L-dopa tolerance and response between Filipinos and Caucasians with Parkinson's disease, with the racial differences in RBC-COMT activity is discussed.