~68% in plasma containing 100µg/L: 94% in plasma containing 5,000µg/L %
||Human Homo sapiens
||Rizzo V, Memmi M, Moratti R, Melzi d'Eril G, Perucca E. Concentrations of L-dopa in plasma and plasma ultrafiltrates. J Pharm Biomed Anal. 1996 Jun14(8-10):1043-6. p.1045 right column 3rd paragraphPubMed ID8818013
||P. 1043 right column: "A rapid, sensitive and specific procedure for the separation of free L-dopa from protein-bound L-dopa in human plasma and subsequent high performance liquid chromatography (HPLC) determination has been recently developed by this group [ref 3]. In the present study, this method was applied to the evaluation of factors affecting L-dopa binding to plasma proteins in vitro."
||P.1045 right column 3rd paragraph: "In all sets of samples examined, L-dopa concentrations were consistently lower in plasma ultrafiltrates than in plasma, indicating a significant degree of protein binding. The unbound fraction appeared to be influenced by the total concentration originally present in the sample and increased from an average of about 68% in plasma containing 100 µg/L L-dopa to 94% at 5000 µg/L. These concentrations are within the range observed in patients with Parkinson's disease receiving chronic treatment with the drug [ref 4]. It should be noted that experiments were carried out in vitro, and that the therapeutic situation in vivo may differ due to potential binding interference by concurrently present metabolites. In this study, however, increasing concentrations of the metabolite 3-OMD (3-O-Methyldopa) were not associated with changes in the degree of L-dopa protein binding in spiked samples."