Researchers have been exploring whether a medicine called zonisamide, which is already used for other conditions such as epilepsy, might help protect the brain in people at high risk of developing Lewy body disease, a condition that includes both Parkinson’s disease and dementia with Lewy bodies. Lewy body disease often begins with subtle symptoms years before a formal diagnosis. This early stage, known as the prodromal phase, is characterised by non-motor warning signs like changes in sleep, mood or sense of smell. In a recent Japanese pilot study, 29 people aged between 50 and 80 who showed at least two early warning signs of the disease and had abnormal brain or heart scans were enrolled. None of the participants had Parkinson’s disease or dementia at the start of the study. They were randomly assigned to re-ceive either the medication or a placebo for around two years. The main question was whether zonisamide could slow changes in brain scans that measures dopamine activity.
Unfortunately, the results showed no meaningful difference between the two groups. Other measures, such as heart imaging and tests of movement and thinking, also did not show clear benefits. Interestingly, two people in the placebo group went on to develop Parkinson’s disease during the study, while those taking zonisamide did not, however this finding needs to be interpreted with caution because the study was very small. Some side effects were reported more often in the zonisamide group, including sleepiness, fatigue, loss of appetite and constipation. Non-motor symptoms, such as mood or sleep problems, also tended to worsen with the drug. Overall, the study did not provide strong evidence that zonisamide can prevent or delay Lewy body disease, but it offers important lessons for designing future trials for preventive Lewis body disease trials.