Dopamine agonists for Parkinson’s: a simple introduction
PD in Practice
Author: Saskia MairPublished: 18 June 2020
Prep: Cook: Serves:
Dopamine agonists are often prescribed to treat Parkinson’s – but how much do you know about them? Our introductory guide answers common questions about the medication, with expert insights from Professor Nicola Pavese
What is a dopamine agonist and how does it work?
Dopamine agonists are a type of medication often used to treat Parkinson’s. Dopamine agonists mimic the action of dopamine – a type of neurotransmitter (a chemical which sends messages across the body) that coordinates movement. It is also linked to other factors, such as motivation, addiction, attention, sleep and heart rate.
“Dopamine agonists are molecules that have a chemical structure and pharmacological action similar to dopamine but have the advantage of easily crossing the blood-brain barrier and act directly on the sites of action of dopamine (dopamine receptors). They are therefore used to replace the missing dopamine in the brains of people living with Parkinson’s.”
Pavese says: “Dopamine agonists are very effective but somehow less effective than levodopa medication (for example Sinemet and Madopar), which is the precursor of dopamine and, once it has crossed the blood-brain barrier and been taken up by the neurons, is converted into dopamine itself.
“Therefore dopamine agonists can be used in the early stage of the disease as the main treatment (monotherapy) to control mild to moderate symptoms of the disease, or later on in more advanced stages, as an adjunct (supplementary) therapy to levodopa, to keep the doses of levodopa low and try to mitigate some of the motor complications that occur in these patients, such as ‘off’ periods.
“Apomorphine, for example, is a powerful dopamine agonist that can be injected subcutaneously (under the skin) to promptly improve sudden ‘off’ periods or early morning dystonia.”
“The side effects of currently available dopamine agonists are generally mild and very similar to those caused by levodopa preparations,” says Pavese. “Compared to levodopa, there is a slighter higher risk to develop excessive daytime sleepiness, impulse control disorders, and, especially in elderly patients, hallucinations and psychosis. These side effects can be slightly different among the different types of dopamine agonists.
“In these cases, the reduction of doses or the progressive weaning off of the implicated dopamine agonist improves the symptoms. Re-adjustments with possible increases in the doses of levodopa are then possibly required.”
These include apomorphine, ropinirole and pramipexole. Some forms also have branded names.
Patient Information Leaflets and the Summary of Product Characteristics can tell you more about individual types of dopamine agonists.
Dopamine agonists can be administered in different ways – orally, transdermal (through a patch) and subcutaneously (injected).
Pavese says that different patients may be prescribed different forms of the medication: “Oral or transdermal dopamine agonists are generally prescribed to younger patients in the early stages of the disease with mild to moderate symptoms, or to more established patients as an adjunct to levodopa preparations to provide a better control of motor symptoms without significantly increase the doses of the former.
“In these cases, the advantage of dopamine agonists is that they are all available in long-acting preparations that can be taken once a day. In more advanced patients with motor fluctuations, apomorphine is administered through a subcutaneous pump that provides a continuous delivery of the drug during the day and a better control of the motor symptoms.”
How could the use of the medication change or evolve in the future?
Pavese says that in the future there could be greater potential to personalise Parkinson’s treatments based on the needs of individual patients.
In terms of dopamine agonists, “improved molecules with properties and activities closer to those of dopamine itself could lead to better clinical improvements with less side-effects.”
He adds: “Pharmacological research is very active in this field, and a number of clinical trials with new promising medications for Parkinson’s are currently ongoing. Participations in these trials might not bring a direct benefit to individual participants but might help the development of new effective treatments for the disease. I therefore encourage patients to consider the possibility to take part in these clinical trials, if available to them.”
Professor Nicola Pavese studied at Pisa University, Italy, and Imperial College London, UK. He is currently a professor of clinical neuroscience and the director of the Clinical Ageing Research Unit at Newcastle University, UK, and is consultant neurologist at Newcastle upon Tyne Hospitals NHS Foundation Trust. His research focuses on neuroimaging in neurodegenerative conditions.
Quick guide to dopamine agonists
Dopamine agonists are Parkinson’s medications used to treat symptoms of the condition. There are several different kinds of dopamine agonists and they can be administered in different ways. Dopamine agonists have been associated with side effects, including sleepiness, nausea and headaches, hallucinations and impulse control disorders.
To find out more about dopamine agonists and other Parkinson’s treatments, please visit the EPDA website here.
JK Rowling praised for joining fight against Parkinson’s
The Harry Potter author has donated £15.3m
19 hours ago
Regular exercise may slow progression of early Parkinson’s disease symptoms
A research team in Japan has suggested that around four hours of weekly moderate exercise is associated with a better clinical course of early-stage Parkinson’s. Their study, published in ‘Neurology’, drew on data from 237 people with the condition, whose symptoms were monitored over a period of up to six years. The research showed that people who were regularly active for at least one to two hours, one or two days a week, were better able to maintain daily activities than those who exercised less – and even experienced a “slower deterioration of processing speed”. The researchers highlighted that these benefits stemmed from maintaining regular exercise over time, rather than levels of activity at the onset of the condition. They added that their findings “suggest it may never be too late for someone with Parkinson’s to start an exercise programme”.
Could traumatic brain injury accelerate the onset of Parkinson’s disease?
Undergoing a traumatic brain injury (TBI) – a sudden injury that damages the brain – may be linked to Parkinson’s onset at an earlier age, new research suggests. The study, led by researchers in the US, examined data from the National Alzheimer’s Coordinating Centre (NACC) database and assessed whether TBI was associated with age of disease onset, survival and the degeneration of dopamine-producing nerve cells in the brain. They found that while there was no significant association with age of death or greater impact on dopamine-producing nerve cells, results showed that TBI was linked to a 4.9-year earlier age of Parkinson’s onset. Reflecting on the results, the researchers wrote that traumatic brain injury “appears to accelerate Parkinson’s onset without altering age of death”. However, the researchers also cautioned that “the nature of this relationship remains unclear”.
NASA astronaut who lived with Parkinson’s disease has died
“When I got diagnosed with Parkinson’s I thought it was over,” US astronaut Michael “Rich” Clifford once said, in a webcast conversation with Parkinson’s expert Dr Ray Dorsey. But when US space agency NASA offered him another opportunity to board a space shuttle, despite the onset of Parkinson’s symptoms, he didn’t hesitate. “And it was as easy as that.” Now, nearly 30 years since his final venture into space, Clifford has died due to complications from Parkinson’s disease. He leaves a legacy of three journeys into space, several awards for his services to the space programme – including the NASA Space Flight Medal – and a history of advocacy for people with Parkinson’s. In a 2013 conversation with the Michael J Fox Foundation, Clifford said: “Everyone with Parkinson’s handles it differently. Don’t let it get in the way of living. “Life is too good. Keep going. The sky’s the limit.” Image credit:…