Interference of levodopa and its metabolites with colorimetry of uric acid.
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.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000097:blood; D003124:Colorimetry / Q000379:methods; D004298:Dopamine / Q000097:blood; D006719:Homovanillic Acid / Q000097:blood; D006801:Humans; D007980:Levodopa / Q000097:blood* / Q000627:therapeutic use; D010300:Parkinson Disease / Q000097:blood; D014527:Uric Acid / Q000097:blood*
D015102:3,4-Dihydroxyphenylacetic Acid; D014527:Uric Acid; D007980:Levodopa; D004298:Dopamine; D006719:Homovanillic Acid