Sometimes patients treated for Parkinson’s disease can have problems with memory and learning. This is thought to be due to a decrease in their dopamine levels due to their disease. Dopamine is a naturally occurring chemical in the brain. Patients with Parkinson’s disease are given many drugs to increase their dopamine levels back to normal, one of which is called Levodopa. Levodopa is converted into dopamine and helps with many of the symptoms of Parkinson’s disease. It has also been found to have effects on memory, improving memory when given after learning.

What are the main aims of the study?

This study is looking to see if Levodopa will improve memory in people without Parkinson’s disease. It will compare participants’ memory performance when on a drug called Madopar (which contains Levodopa) with your performance when on a placebo (a vitamin pill), to see if Levodopa improves memory retrieval in healthy older adults.

What does it involve for a participant?

Participants in this study will have four visits (2 x two consecutive days) at the Bristol Brain Centre, which is located at Southmead Hospital.

On one of the days a dose of Madopar will be given to participants, a drug which is a commonly used to increase levels of dopamine in the brain. This will be taken together with an anti-sickness drug.

On day 1 the participants will take part in two computer based tasks. One of these tasks will provide the opportunity to win or lose money (participants will be given a starting ‘stake’ so will therefore not be at risk of losing any of their own money). The task is designed so that participants will receive more money if they do better than if they do poorly. The maximum win is £10 on each visit (£40 in total). The second test is a verbal memory test.

On day 2 participants will receive the drugs or a placebo. They will first be given Domperidone which will prevent any nausea that may occur from the other drug.

Hanna Isotalus, Study Coordinator for the DARet Study

Hanna Isotalus, Study Coordinator for the DARet Study

They will then be given Madopar. Heart rate and blood pressure will be monitored and once the Madopar has taken effect after roughly 60 minutes, participants will be asked to complete a short test of the word list and the reward task that they learnt on day 1. Participants will then learn another list of words and their memory of this list will be tested as well. During the visits, there will also be a few short questionnaires asking about sleep and general mood.

We will then phone participants 1 day, 3 days and 5 days after this visit to ask about the second word list that they learnt. We can arrange these phone calls to suit people’s individual schedules. Days 3 and 4 will follow a similar structure to days 1 and 2, with the exception that on one of the days you will receive a placebo and on the other, the drug. This study is double-blind which means that neither we nor you will know which day you will receive the drug on. You will only receive Madopar and Domperidone once.

The visits on days 1 and 3 will take approximately 1 hour and 15 minutes. The visits on days 2 and 4 will take approximately 2 hours and 30 minutes. There will be at least 7 days between days 1 and 3, but it does not need to be exactly 7 days.

There is a small risk of increased sleepiness from the drugs so we will ask participants that they do not drive home after the sessions on days 2 and 4 (you are fine to drive to these sessions, and to and from the day 1 and 3 sessions). We also advise that participants do not drive or operate any heavy machinery for 4.5 hours after the sessions on days 2 and 4, until the drug has left the system. Taxis can be provided if you live within the Bristol area.

How long is the study for?

This study involves four visits to the Bristol Brain Centre which will comprise of 2 x two consecutive days. There will also be a series a phone calls as part of the study and these can be arranged to suit the participants’ schedule.

What do you hope the outcomes of the study will be?

Previous studies show that increasing dopamine activity might improve memory and learning from rewards. This study will look into the different memory processes and we hope to find out if taking a pill that increases dopamine activity will improve the ability to access stored memories.

Where is the study based?

The study is based at the Bristol Brain Centre, which is located at Southmead Hospital, Bristol.


o        This study is looking for people over the age of 65 without memory problems.

o        As participants will be studying word memory, you will need to be a native English speaker to take part.

o        Due to the nature of this study, we have very specific exclusions on who is eligible to take part for safety reasons. If any of these apply to you, you may not be eligible (if you are unsure, please get in touch):

  • You have a diagnosed sleep/neurological/psychiatric condition
  • You have unstable diabetes, lactose intolerance, a history of malignant melanoma, peptic ulcer, osteomalacia, galactosemia, intention tremor, prolactinoma, suspicious undiagnosed skin lesions, electrolyte disturbances, prolongation of cardiac conduction, or severe endocrine, liver, kidney, lung or heart disorders
  • You take medications that are known to interfere with Madopar, or Domperidone. (If you express interest in taking part in this study, we will ask you about the medication you take to make sure this does not apply to you)
  • You have a known sensitivity to Levodopa, Benserazide or Domperidone


You can see if you are eligible for this study, as well as others around the nation, by logging into your Join Dementia Research account.

Not registered with Join Dementia Research? Why not sign up today?