Effects of levodopa on pulmonary function in Parkinson's disease

Study objectives: Upper-airway obstruction (UAO) may be present in patients with Parkinson's disease (PD), and its reversibility after levodopa therap y has been suggested. To investigate the effects of oral intake of levodopa on pulmonary function and UAO criteria in patients with PD, we studied 22 patients with PD. Design: Pulmonary function tests were performed after a 12-h withdrawal of levodopa therapy, and 1 h after oral intake of placebo or levodopa, accordi ng to a double-blind, placebo-controlled, crossover study. Six: UAO criteri a were recorded to detect UAO in patients. UAO was found in 5 of 21 patient s on baseline conditions (1 patient could not perform all tests). Results: Among the patients with UAO, after levodopa therapy three of five patients did not meet the four of six required criteria for defining UAO. L evodopa produced its effects on UAO criteria by means of a saw-tooth patter n improvement and/or a decrease below the defined thresholds of the peak in spiratory flow and the FEV1/peak expiratory flow (PEF) and FEV1/forced expi ratory flow after 50% of the FVC (FEV0.5) ratios. Levodopa PEF increased by 0.85 L/s in patients with UAO and by 0.24 L/s in patients without UAO, whi le after placebo it increased by 0.03 L/s in patients with UAO and decrease d by 0.16 L/s in patients without UAO (p = 0.02). Whereas in patients witho ut UAO an increase of the FEV1/PEF and FEV1/FEV0.5 ratios was observed afte r placebo and levodopa intake, these ratios decreased after levodopa and in creased after placebo in patients with UAO. Conclusions: These results show that levodopa administration in patients wi th PD induces significant variations in PEF and UAO ratios (FEV1/PEF and FE V1/FEV0.5).