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Clinical Chemistry, Vol 27, 756-758, Copyright © 1981 by American Association for Clinical Chemistry
DW Bierer and AJ Quebbemann
Reportedly, levodopa (L-DOPA) administration produces spuriously high values for plasma uric acid as measured by the commonly used phosphotungstic acid-hydroxylamine colorimetric method. We confirm this interference, not only by L-DOPA but also by three of its major metabolites: dopamine, 3,4-dihydroxyphenylacetic acid, and 3-methoxy-4- hydroxyphenylacetic acid. However, at therapeutic concentrations in plasma (less than 5 mg/L), the maximum spurious uric acid concentration due to L-DOPA is less than 2 mg/L. Also, at reported peak plasma concentrations of L-DOPA plus three of its major metabolites, the maximum spurious uric acid concentration due to all four compounds combined is less than 8.5 mg/L. Therefore, the hyperuricemia observed with this method in some patients who are chronically receiving L-DOPA cannot be attributed only to interference by L-DOPA and its metabolites in the colorimetric determination of uric acid. Evidently L-DOPA may increase laboratory values for plasma uric acid concentrations, both by pharmacological and chemical mechanisms.
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