Anti-nausea Medicine Ondansetron Will Be Tested for Treating Hallucinations

Ondansetron, an anti-nausea medication usually prescribed to those undergoing cancer therapies, will be tested in an upcoming Phase 2 clinical trial as a possible treatment for visual hallucinations associated with Parkinson’s disease.

The study (NCT04167813) — officially the Trial of Ondansetron as a Parkinson’s Hallucination Treatment, or TOPHAT — is being funded by the charity organization Parkinson’s U.K., in partnership with the University College London (UCL).

TOPHAT will assess the safety and effectiveness of ondansetron, compared with a placebo, at reducing hallucinations in 216 people with Parkinson’s who experience visual hallucinations at least once each week. Recruitment has not yet started; more information about potential participation in the trial can be found here and here.

Following enrollment, patients will be randomly assigned to receive ondansetron or the placebo, both administered at home at increasing daily doses, ranging from 8–24 mg, for 12 weeks. After completing this course of treatment, the participants will be followed for a further 12 weeks.

In addition to evaluating ondansetron’s ability to reduce visual hallucinations, investigators will assess the therapy’s effects on delusions and other Parkinson’s symptoms, such as tremors, anxiety, and sleep problems. Assessments will be made after six and 12 weeks of treatment.

Ondansetron already is approved for use — marketed as Zuplenz, Zofran ODT, and Zofran — by the U.K.’s National Health Service (NHS) as a treatment for nausea and vomiting caused by chemotherapy. If shown to be safe and effective in TOPHAT, it may become available through the NHS without the need for further clinical studies.

“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,” Arthur Roach, PhD, director of research at Parkinson’s U.K., said in a press release.

“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,” Roach said.

Hallucinations — seeing, hearing, or feeling things that are not real — can have a significant impact on one’s quality of life. Different studies have estimated that 8–40% of people with Parkinson’s who are undergoing long-term treatment will experience hallucinations at some point in their lives. This percentage can rise to as high as 76% as the disease gradually progresses, meaning three of every four Parkinson’s patients may experience hallucinations.

Patients and carers alike feel the strain of hallucinations — often accompanied by delusions, or false beliefs — which add stress to personal relationships. Treating these symptoms is challenging, as the only available medications are anti-psychotics that can worsen other Parkinson’s symptoms and cause unwanted side effects.

“My hallucinations have started to increase in the past few months and I want them to settle down,” said Michelle Ellis, of Leicestershire, a 54-year-old who was diagnosed with Parkinson’s in 2012 and had her first hallucination four years later.

“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,” Ellis said.

TOPHAT is taking place at a crucial time, according to Parkinson’s U.K. The non-profit recently conducted a nationwide survey that found that one in 10 respondents said their hallucinations had worsened during the COVID-19 pandemic. Moreover, nearly half (48%) of respondents who received social care and support at home before the COVID-19 lockdowns reported getting less care during the restrictions.

Because of the pandemic, TOPHAT has been designed to accommodate social distancing measures. Researchers will conduct most consultations either by telephone or video, limiting in-person assessments to only those needed for essential blood tests and electrocardiograms.

The trial is being funded by Parkinson’s Virtual Biotech, the drug development arm of Parkinson’s U.K. This program provides funding to fast-track projects with the greatest scientific potential to improve the lives of people with Parkinson’s.