Is there a difference in gastric emptying between Parkinson’s disease patients under long-term l-dopa therapy with and without motor fluctuations? An analysis using the ¹³C-acetate breath test

The mechanism underlying the motor fluctuations that develop after long-term l-dopa therapy is not fully known. It has been speculated that malabsorption of l-dopa from the small intestine occurs. It was reported that gastric retention in Parkinson’s disease (PD) patients with motor fluctuations is increased as compared with that in PD without fluctuations. Because l-dopa therapy may worsen the symptoms of delayed gastric emptying (GE), it was not clear whether the delayed GE of PD patients with motor fluctuation was affected by l-dopa therapy. We assessed GE in PD patients with and without motor fluctuations. We investigated GE in 40 patients with PD under long-term l-dopa therapy, 20 fluctuators with “delayed-on” and “no-on” phenomena, 20 nonfluctuators, and 20 healthy volunteers. GE was examined by the ¹³C-acetate breath test (¹³C-ABT) [the half emptying time (HET), the peak time of the ¹³C-%-dose-excess curve (T _max)], with expirations collected for 4 h after a test meal and analyzed for ¹³CO₂ using an infrared (IR) spectrophotometer. The T _max of GE as assessed using the ¹³C-ABT was significantly delayed in all PD patients as compared with controls (P = 0.002). The HET was significantly delayed in all PD patients as compared with controls (P < 0.001). The T _max and HET were not significantly delayed in PD patients with motor fluctuations as compared with PD patients without motor fluctuations. These results demonstrated that GE is commonly delayed in PD patients with long-term l-dopa therapy. Delayed GE does not differ between PD patients with and without motor fluctuations. This finding demonstrated that the motor fluctuation in PD may not be influenced by GE.