Gastrointestinal Involvement in Parkinson Disease and Its Impact on Levodopa Efficacy: Laren Becker, MD, PhD

WATCH TIME: 7 minutes

"The main point is that gastrointestinal involvement can have serious implications for PD therapy. It must be considered, especially when individuals aren’t responding appropriately to treatment."

Recent studies have shown that gastrointestinal (GI) disorders are frequently observed in patients living with Parkinson disease (PD) and may impact the absorption of oral levodopa, which could potentially contribute to motor fluctuations or OFF periods. Studies have also revealed that conditions such as delayed gastric emptying (gastroparesis) and Helicobacter pylori infection are commonly reported in PD and have been associated with symptoms like nausea, bloating, and gastritis. Thus, research suggest these GI issues may be linked to delayed levodopa absorption and variability in treatment response for patient with PD.¹

These challenges were the focus of a non-CME panel event sponsored by Merz Therapeutics at the recently concluded 4th Annual Advanced Therapeutics in Movement and Related Disorders (ATMRD) Congress, held by the PMD Alliance from June 27-30, 2025. The session centered on how gastrointestinal dysfunction in PD can contribute to the unpredictability and variability of oral baseline carbidopa/levodopa therapy. Expert panelists included Ramsey (Drew) Falconer, MD, a movement disorder specialist at Inova Parkinson’s and Movement Disorders Center, and Laren Becker, MD, PhD, assistant professor of medicine in the Division of Gastroenterology at Stanford University, who shared strategies for optimizing OFF episode management with on-demand therapy.²

Following the session, Becker spoke with NeurologyLive^® to further discuss how emerging insights into the peripheral effects of PD, particularly those involving the GI system, may reshape clinical understanding and treatment approaches. He explained that key dopaminergic enzymes are present not only in the brain but also in the gut, which can complicate levodopa delivery. Becker also reviewed the progression of GI dysfunction in PD, including impaired swallowing, delayed gastric emptying, and widespread constipation. These findings, he noted, underscored the need for comprehensive, gut-focused approaches to improve care for individuals with PD.

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REFERENCES
1. Pfeiffer RF, Isaacson SH, Pahwa R. Clinical implications of gastric complications on levodopa treatment in Parkinson's disease. Parkinsonism Relat Disord. 2020;76:63-71. doi:10.1016/j.parkreldis.2020.05.001
2. Becker L, Falconer R. Overcoming Gastrointestinal Barriers: Acute OFF Episode Management in PD. Presented at: ATMRD; June 27-30, 2025; Washington, DC.