Cancer anti-sickness drug offers hope for hallucinations in Parkinson's

A world-first double-blind clinical trial will investigate if a powerful drug used to treat nausea in chemotherapy patients could alleviate hallucinations in people with Parkinson's. 

Parkinson's UK, the largest charitable funder of Parkinson's research in Europe, is partnering with UCL, and investing £1 million in a pioneering phase 2 clinical trial to explore if the drug ondansetron is safe and effective against hallucinations.

There are currently 145,000 people living with Parkinson's in the UK and 75% of them will experience visual hallucinations at some point.

The trial comes at a crucial time as a survey carried out by the charity worryingly found that 1 in 10 people with Parkinson's reported an increase in hallucinations during lockdown, which led to an increase in calls to their helpline.¹

The funding for this 4-year project comes via the charity’s drug development arm, the Parkinson's Virtual Biotech. Launched in 2017, the innovative programme is plugging the funding gap to fast-track the projects with the greatest scientific potential to transform the lives of people with Parkinson's.

This is the second clinical trial to be added to the Virtual Biotech's pipeline of projects in a drive to develop better drug treatments for people with Parkinson's.

Dr Arthur Roach, Director of Research at Parkinson's UK, said:

"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.
"With the support of Parkinson’s UK, UCL has been rapidly adapting the research during the pandemic, to enable us to drive forward and launch this promising trial, which marks another milestone in our thriving Parkinson's Virtual Biotech programme."

Hallucinations in Parkinson's

Treating hallucinations is one of the most challenging aspects in people with Parkinson's and it can have a big effect on their quality of life. It can be extremely distressing for carers as well as people with Parkinson's, putting stress on relationships.

The only medications available to treat it today are anti-psychotic drugs which can worsen Parkinson's symptoms and potentially cause serious side effects. This urgent need for new treatments is why hallucinations are a top priority for the Parkinson's Virtual Biotech.

The 12-week, double-blind, placebo-controlled trial is set to recruit 216 people over 2 years in 20 to 25 NHS clinics across the UK. Patients will be randomised to receive either drug or placebo tablets, to take at home for 12 weeks. To accommodate social distancing, researchers will conduct the majority of the study via video or telephone consultations, with face-to-face assessments limited to only 3 for essential blood tests or ECGs.

Visual and other types of hallucinations, as well as delusions (false beliefs), will be assessed after 6 and 12 weeks of treatment, along with Parkinson's related motor and non-motor symptoms. 

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

"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. 

"Ondansetron influences visual processing in the brain and its potential for treating visual hallucinations in Parkinson's was first identified in small studies in the early 1990s.

"This trial will enable us to find out if ondansetron is effective and safe as a treatment and if it is, we could see clinicians prescribing an inexpensive drug with fewer side effects to people with Parkinson's throughout the UK."

"My hallucinations have become worse"

Michelle Ellis, 54, from Ashby-de-la-Zouch, Leicestershire, was diagnosed with Parkinson's at the age of 46 in 2012. She experienced her first hallucination 4 years later.

Michelle said:

"One evening, returning from visiting a friend, we pulled into a service station. My husband was driving and my 7-year-old granddaughter, Amy, was in the car. I turned around to see if she was asleep, and I saw someone sitting next to her. I told my husband, 'Stop the car, someone is in the back with Amy.' I was convinced. But my husband promised me nobody was there. I felt very frightened. My hallucinations always featured random people who were walking around the house and they were happening daily so it was quite terrifying."
Michelle saw a specialist nurse 2 years ago who lowered her Madopar medication and the hallucinations stopped. They were few and far between however, in the past few months they have become more frequent. Michelle continues to see movement and shadows out of the corner of her eyes and is worried about what this means for the future.
"My hallucinations never really went away and have become worse. I am worried because they 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."

To find out how to sign up to the trial, visit  


Media enquiries 

For further information/case studies/interview requests please contact:

Parkinson’s UK

Anita Salhotra, Senior Media and PR Officer at Parkinson's UK:

020 7932 1361 / 07812 737 697 or [email protected] 

Out of hours: 07961 460 248 or [email protected]   


Chris Lane, UCL Media Relations:

020 7679 9222 / 07717 728 648 or [email protected] 

Notes to editors

¹The survey was conducted during April and May 2020.

The survey sample was of 2,031 people, made up of 1,491 people with the condition and 540 family members, friends and carers. 

For the full methodology and copy of the full report, see the Parkinson's UK website

About Parkinson’s UK

Anyone can get Parkinson's, young or old. In the UK, around 145,000 people are already living with Parkinson's. Every hour, 2 more people are diagnosed.

Parkinson's is what happens when the brain cells that make dopamine start to die. There are over 40 symptoms, from tremor and pain to anxiety. Some are treatable, but the drugs can have serious side effects. It gets worse over time and there’s no cure. Yet.

We're the largest charitable funder of Parkinson's research in Europe. We know we’re close to major breakthroughs. By funding the right research into the most promising treatments, we get closer to a cure every day.

Until then, we're here for everyone affected by Parkinson's. Fighting for fair treatment and better services. Making everyone see its real impact. 

We are Parkinson's UK. Powered by people. Funded by you. Together we'll find a cure.

Advice, information and support is available via our website,, or our free, confidential helpline on 0808 800 0303

About the Parkinson's Virtual Biotech

People with Parkinson's urgently need new treatments. But right now, there’s a huge gap in drug development. The Parkinson's Virtual Biotech exists to bridge that critical funding shortage. 

It takes the most promising research and partners with institutions and pharmaceutical companies worldwide to develop the findings into plausible drug treatments. Currently there are projects at the discovery, preclinical and early clinical development stages.

With no large teams of scientists or expensive labs to run, the Parkinson's Virtual Biotech ensures that every penny of the annual £4m investment goes on what matters most: fast tracking the projects with the greatest potential to transform the lives of people with Parkinson’s.

No one else is doing this. It's a bold risk. But we believe it will deliver a groundbreaking new treatment by 2024. Because people with Parkinson's won't wait. Together, we'll find a cure.

To find out more, visit

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