Canadian trial finds common medicine may aid memory in Parkinson's-related dementia cases
A common European cough medicine may help protect the brain in Parkinson’s-related dementia, but its cognitive effects appear limited to a genetically defined subgroup, according to a Canadian-led clinical trial published in JAMA Neurology.
As reported by CTV News, researchers at Lawson Health Research Institute conducted a year-long study involving 55 participants diagnosed with mild to moderate Parkinson’s disease dementia (PDD).
Participants received either high-dose or low-dose Ambroxol, or a placebo. Psychiatric symptoms worsened in the placebo group but remained stable in those receiving Ambroxol.
A key brain damage biomarker, GFAP, increased in the placebo group but held steady with Ambroxol.
Stephen Pasternak, lead investigator and cognitive neurologist at Parkwood Institute, stated, “We saw that patients on the placebo had worsening of psychiatric symptoms.”
He added, “We saw a small subgroup of patients have improvements in cognition,” particularly those with GBA1 gene variants.
Ambroxol boosts the GCase enzyme, which is deficient in many Parkinson’s patients. A deficiency in GCase is linked to the build-up of waste in brain cells.
According to Neuroscience News, three of five GBA1 carriers treated with Ambroxol improved by at least 3 points on the ADAS-Cog-13 cognitive scale, while three of four showed clinically meaningful gains on the Neuropsychiatric Inventory.
Despite these individual improvements, the overall trial did not show differences in cognitive scores between the Ambroxol and placebo groups at 26 or 52 weeks, as per MD Page Today.
Pasternak and colleagues wrote that “primary outcome measures did not support therapeutic effects of ambroxol on cognition,” though the stabilisation of neuropsychiatric symptoms and brain damage markers suggests other potential benefits.
Ambroxol reached therapeutic levels in the brain and was generally safe, although gastrointestinal side effects were more common in the Ambroxol group (12 percent) than placebo (5 percent), as reported by MD Page Today.
While Ambroxol is not approved in Canada or the US, it has been used for decades in Europe for respiratory conditions, including at high doses and during pregnancy.
Pasternak first encountered Ambroxol during a fellowship at SickKids Hospital in Toronto, where it was used to treat Gaucher disease—a childhood disorder tied to GCase deficiency.
The trial was funded by the Weston Foundation and, according to Neuroscience News, sets the stage for a follow-up trial focused specifically on cognitive outcomes and GBA1 carriers.
Pasternak noted, “Our goal was to change the course of Parkinson’s dementia,” and said the findings “provide a strong foundation for larger studies.”
According to CTV News, dementia develops in about half of Parkinson’s patients within 10 years, adding pressure to health systems seeking treatments that go beyond symptom relief.
While current therapies only address symptoms, Pasternak stated that the hope is to “give [patients] a safe, easy way to take medication, which would prevent the development of these diseases.”
