Summary
Effects of the chronic administration of levodopa on its peripheral pharmacokinetics and the contribution of the pharmacokinetics to the pathogenesis of the wearing-off phenomenon are re-evaluated. The concentration of plasma levodopa and clinical symptoms were determined 4 hours after oral levodopa (levodopa 100 mg+benserazide 25 mg) administration on 55 parkinsonian patients. Long-term levodopa therapy markedly increased the peak levodopa concentration (Cmax) and the area under the time-concentration curve (AUC); whereas, it decreased time to the peak concentration (Tmax) and the elimination half-life (T1/2). These results suggest that longterm levodopa therapy accelerates the absorption of levodopa. The wearingoff group (n=23), however, had a markedly higher Cmax and AUC, and a shorter Tmax and T1/2 than the stable group (n=32). We speculate that the clinical expression of “stable” or “wearing-off” depends on the absorption of levodopa as well as the presynaptic terminal and post synaptic receptors.
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Murata, M., Mizusawa, H., Yamanouchi, H. et al. Chronic levodopa therapy enhances dopa absorption: Contribution to wearing-off. J. Neural Transmission 103, 1177–1185 (1996). https://doi.org/10.1007/BF01271202
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DOI: https://doi.org/10.1007/BF01271202