Effect of acute levodopa challenge test on cerebral blood flow in Parkinson's disease with the supine-to-standing transcranial Doppler test

Background: Levodopa, a common drug that improves symptoms of Parkinson's disease (PD), can induce a reduction in blood pressure (BP); however, the effect of levodopa on cerebral blood flow (CBF) remains unclear.Objectives: To observe the changes in BP and CBF during active standing before and after the acute levodopa challenge test (ALCT) and analyse the influencing factors of CBF in patients with PD.Methods: BP and CBF velocity were simultaneously recorded by continuous beat-to-beat non-invasive BP monitoring and transcranial Doppler at supine and orthostatic positions twice, before and after ALCT. The pa-tients were divided into two groups according to those with increased and decreased CBF at baseline after ALCT to analyse the influencing factors.Results: We examined 64 patients with PD (59.2 +/- 11.6 years, 33 males). BP decreased at all timepoints after ALCT, while there was no significant change in the magnitude of the drop in BP induced by standing. CBF was reduced after ALCT, especially within 15 s to 1 min of standing (15 s: 48.95 +/- 13.50 vs. 44.93 +/- 13.26, p < 0.001; 30 s: 52.46 +/- 12.06 vs. 50.11 +/- 12.56, p = 0.033; 1 min: 52.19 +/- 11.83 vs. 50.17 +/- 13.21, p = 0.044). Lower body mass index (beta = -0.280, p = 0.027) was an independent factor associated with CBF reduction after ALCT.Conclusions: Additional attention should be paid to changes in CBF and BP within 1 min after standing in patients with PD taking levodopa, especially in those with low bodyweight.