Could an anti-sickness drug treat hallucinations in Parkinson's?

Ondansetron is an anti-sickness medication, usually used for people having cancer treatment. This trial will explore whether it can effectively treat visual hallucinations in people with Parkinson's. 

The Trial of Ondansetron as a Parkinson's Hallucination Treatment (TOP HAT) will run in partnership with UCL. The £1m phase 2 clinical trial will test the drug against a placebo (dummy treatment) in 216 people with Parkinson's who experience hallucinations.

We've been working with UCL and research volunteers to rapidly adapt this project during the pandemic. To minimise risk, and help participants to feel safe, researchers will conduct the majority of the study via video or telephone consultations. 

If this research shows that ondansetron is safe and effective, it could be made available to people with Parkinson's on the NHS without the need for further studies. This could mean a vital new treatment in just a few years.

Hallucinations in Parkinson's

There are currently 145,000 people living with Parkinson's in the UK and 75% are likely to experience visual hallucinations at some point. Either because of their condition or as a side effect to medications to treat other symptoms of Parkinson's. Hallucinations are when people see, hear or feel things that aren’t really there. 

Hallucinations can have a big impact on quality of life, as well as being frightening for people with Parkinson’s and their families. There are currently no specific treatments approved in the UK for people with Parkinson's who experience this distressing symptom. 

This trial comes at a crucial time. In a recent survey conducted by Parkinson's UK and researchers at the University of Lancaster, 1 in 10 respondents reported that hallucinations had worsened during the COVID-19 pandemic. Read more about the survey results.

Michelle Ellis, 54, from Ashby-de-la-Zouch, Leicestershire, was diagnosed with Parkinson’s in 2012. She was just 46 and experienced her first hallucination 4 years later. 

Michelle says:

"My hallucinations have started to increase in the past few months and I want them to settle down. I tend to dwell on them when I am having a bad day with my Parkinson’s symptoms. It’s very important to have a drug that focuses on treating hallucinations on their own."

Michelle shares more of her experience with vivid hallucinations in this magazine article.

Dr Arthur Roach, Director of Research at Parkinson’s UK, says:

"It’s vital we find better treatments for people with Parkinson’s who have seen their hallucinations worsen at home and ondansetron offers much hope for them and their families.

"If successful, positive results from the trial could see this drug, which is already used in the NHS, quickly repurposed to become an available treatment in Parkinson’s."

Suzanne Reeves, Lead Researcher and Professor of Old Age Psychiatry and Psychopharmacology at UCL, says:

"Visual hallucinations pose a particular challenge in Parkinson’s as the very treatments for motor symptoms in Parkinson’s can also trigger and worsen this distressing symptom. Finding treatments for hallucinations that are both effective and safe is an area of great unmet need."