TOP HAT – Visual Hallucinations

Who may be interested?

If you are seeing things that you know are not there you may be eligible to join this clinical trial.  You or your care partner can make the referral for a consultation.

The study team wants to hear from those living in Cornwall and the Plymouth urban area. All the activities for the participant and care partner are conducted at home and neither of you need to have or be able to use a computer or smartphone.

The first appointment with a study investigator is part of the process to ensure your safe participation; it includes a blood pressure check and a brief memory test. If you are taking Apomorphine or certain anti-sickness medications and they cannot be changed, you won’t be eligible.

What is being trialled ?

Ondansetron, a drug that is already licensed for use as an anti-sickness medication. The study aims to find out if it is effective and well tolerated as a treatment for visual hallucinations in PwPs. Its performance is being compared to placebo, a tablet that looks identical but contains no drug. Neither you nor the local study investigators will know if you are receiving the drug or the placebo.

What is involved?

Three brief face-to-face assessments are part of the trial process. They involve taking a blood sample and an electrocardiogram (ECG) or a blood pressure check, firstly to ensure it is safe for you to take part and then to monitor health and safety while taking the study drug.

The ECG is recorded by this small hand-held device that communicates with the investigator’s smart phone, which in turn sends the information to be stored securely.

Treatment lasts for 12 weeks, with telephone follow up for a further 12 weeks after the treatment ends.

Interested in taking part?

If you are interested or would first like to know more, please contact Richard Higgins on 01209 204020 or email him at Richard is both the contact on behalf of the NHS Trust* and one of the study investigators.  This is his leaflet.


Further Information

Please read the Care Partner Information Sheet  and the Participant Information Sheet for a full description of the Trial, and in particular the excluding conditions.

Background Information

Ondansetron was identified as a promising treatment for visual hallucinations in the early 1990s, in two small studies of 23 PwPs of which 16 were hospitalised because they had persistent severe hallucinations. The drug was effective in reducing visual hallucinations in all but one PwP, with only mild side effects of constipation and headache and no worsening of Parkinson’s symptoms. Further studies were not carried out at the time because the drug was extremely expensive. Costs are now similar to standard treatment and a larger study is timely and necessary.

* Cornwall Partnership NHS Foundation Trust Research Team
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