Influence of the dopamine agonist alpha-dihydroergocryptine on the pharmacokinetics of levodopa in patients with Parkinson's disease

This study investigated whether chronic coadministration of alpha -dihydroe rgocryptine (DHEC) altered the plasma pharmacokinetics of individualized tr eatments with levodopa in 12 patients with Parkinson's disease. Steady-stat e pharmacokinetics of plasma levodopa (L-Dopa) under combined treatment wer e compared with those under treatment with L-Dopa alone. There was no evide nce of increased exposure to L-Dopa caused by concomitant treatment with DH EC. In contrast, additional treatment with DHEC reduced the overall exposur e to L-Dopa (17.5% reduction in area under the curve; 95% Cl: 23%-6%). This effect was small but statistically significant for the area under the plas ma concentration-time curve, whereas t(max) (time of maximum plasma concent ration) and peak-to-trough fluctuation were not affected. C-max (maximum pl asma concentration), on average, was reduced to a similar extent (-14.5%; 9 5% Cl: 38% to -17%), albeit not significantly. The magnitude of the interac tion does not suggest changing the current clinical practice of up-titratin g DHEC and subsequently adapting L-Dopa to the individual needs of patients .