Design
TOPHAT is a double-blind, randomised, placebo-controlled, flexible-dose trial of ondansetron as a treatment for Parkinson’s hallucination, with a 12-week primary outcome and follow-up to 24 weeks.
Aims
The principle aim is to answer the question: ‘Will ondansetron be better than placebo at reducing the frequency and/or severity of visual hallucinations over 12 weeks’?
We will measure this using Scale for Assessment of Positive Symptoms-Hallucinations (SAPS-H) scores.
Secondary aims will answer the following questions:
- ‘Will ondansetron reduce delusions’? This information is important as it is possible that ondansetron’s effects will extend beyond hallucinations
- ‘Will ondansetron be safe and well tolerated in people with Parkinson’s? Side effects were reported in the small studies (headache, constipation) but nobody stopped taking medication. We also wish to establish that ondansetron will not worsen motor, non-motor or cognitive symptoms of Parkinson’s.
- ‘Will ondansetron be cost effective for NHS use’? We will be collecting information on health related quality of life and health and social care resource use
How have people with Parkinson's and their families helped shape Top Hat?
Updates
Recruitment began in November 2021 and in May 2022 eligibility criteria were extended to include people with a related condition, Lewy Body dementia.
Following an interim analysis TOP HAT was temporarily halted as safety data was reviewed. We are delighted to announce that TOP HAT recruitment is due to start again in November 2024 and we are looking for new participating sites! Recruitment of new participants has been extended and will continue until July 2026.
Contact us
If you would like more information about any aspect of the trial or you would like to participate please contact:
o.zubko@ucl.ac.uk and Suzanne.reeves@ucl.ac.uk
Postal address
Wing B, 6th floor
Maple House
149 Tottenham Court Road
London W1T 7NF