Cough medicine turned brain protector? Ambroxol may slow Parkinson’s dementia

Researchers at Lawson Research Institute (Lawson), the research arm of St. Joseph’s Health Care London, are investigating whether Ambroxol — a cough medicine used safely for decades in Europe — can slow dementia in people with Parkinson’s disease.

Published on June 30 in the prestigious JAMA Neurology, this 12-month clinical trial involving 55 participants with Parkinson’s disease dementia (PDD) monitored memory, psychiatric symptoms and GFAP, a blood marker linked to brain damage. Parkinson’s disease dementia causes memory loss, confusion, hallucinations and mood changes. About half of those diagnosed with Parkinson’s develop dementia within 10 years, profoundly affecting patients, families and the health care system.

Led by Cognitive Neurologist Dr. Stephen Pasternak, the study gave one group daily Ambroxol while the other group received a placebo. “Our goal was to change the course of Parkinson’s dementia,” says Pasternak. “This early trial offers hope and provides a strong foundation for larger studies.”

Key findings from the clinical trial include:

• Ambroxol was safe, well-tolerated and reached therapeutic levels in the brain
• Psychiatric symptoms worsened in the placebo group but remained stable in those taking Ambroxol.
• Participants with high-risk GBA1 gene variants showed improved cognitive performance on Ambroxol
• A marker of brain cell damage (GFAP) increased in the placebo group but stayed stable with Ambroxol, suggesting potential brain protection.

Although Ambroxol is approved in Europe for treating respiratory conditions and has a long-standing safety record — including use at high doses and during pregnancy — it is not approved for any use in Canada or the U.S.

“Current therapies for Parkinson’s disease and dementia address symptoms but do not stop the underlying disease,” explains Pasternak. “These findings suggest Ambroxol may protect brain function, especially in those genetically at risk. It offers a promising new treatment avenue where few currently exist.”

Ambroxol supports a key enzyme called glucocerebrosidase (GCase), which is produced by the GBA1 gene. In people with Parkinson’s disease, GCase levels are often low. When this enzyme doesn’t work properly, waste builds up in brain cells, leading to damage. Pasternak learned about Ambroxol during a fellowship at The Hospital for Sick Children (SickKids) in Toronto, where it was identified as a treatment for Gaucher disease — a rare genetic disorder in children caused by a deficiency of GCase.

He is now applying that research to explore whether boosting GCase with Ambroxol could help protect the brain in Parkinson’s-related diseases. “This research is vital because Parkinson’s dementia profoundly affects patients and families,” says Pasternak. “If a drug like Ambroxol can help, it could offer real hope and improve lives.”

Funded by the Weston Foundation, this study is an important step toward developing new treatments for Parkinson’s disease and other cognitive disorders, including dementia with Lewy bodies. Pasternak and his team plan to start a follow-up clinical trial focused specifically on cognition later this year.