Trusted Voices: Behavioural side effects and the challenge of medicines information
This month’s Trusted Voices feature is not about misinformation or inaccurate medicines information. It explores some of the challenges people face understanding and acting on medicines information.
Through a Parkinson’s medication case study, this article looks at behavioural side effects and how the PIF community can work together to improve medicines information.
Parkinson’s medicines and behavioural side effects
Parkinson’s is a progressive neurological condition affecting around 153,000 people in the UK. Many people with Parkinson’s take medicines to help manage symptoms such as tremor, stiffness and movement difficulties. These medicines can greatly improve daily life.
Some Parkinson’s medicines, particularly dopamine agonists, can cause behavioural side effects in some people.
These behaviours can include gambling, compulsive shopping, binge eating or increased sexual urges. Clinically, they are often called “impulse control disorders” or “impulse control behaviours”.
Clinicians, researchers and pharmaceutical companies have been aware of these side effects for more than 20 years. Information about them already exists within medicines guidance and patient information leaflets. However, gaps can still exist between clinical knowledge and patient understanding.
For many people, understanding side effects requires more than a leaflet alone. Medicines information can sometimes feel inaccessible, overly clinical or difficult to navigate. Research has found 1 in 2 people have concerns about the readability of medicines information leaflets and have difficulty judging the advantages and disadvantages of treatment.
BBC investigation
Over the past year, the BBC says it has spoken to many families affected by compulsive gambling, shopping and sexual behaviours linked to dopamine agonist drugs. Some people reported medicines information leaflets do not explain clearly the side effects and how serious they can become, or the warning signs families should look out for.
The BBC explored these issues in the Shadow World podcast series – you can listen here.
What Parkinson’s UK is hearing from families
Parkinson’s UK often hears from people whose lives have been affected by behavioural side effects linked to Parkinson’s medicines.
Siôn Baldwin-Jones, Health Content Lead at Parkinson's UK, says people do not always identify changes in behaviour quickly because they often develop gradually. Feelings of shame or guilt may also stop people talking openly about what is happening. Addictive behaviours are still heavily stigmatised, and this can stop people seeking support early.
Siôn also says some people do not even realise their behaviour has changed. The medication itself can make it harder for people to recognise changes in behaviour, meaning partners, friends or family members often notice changes first.
The challenge of medicines information
In Parkinson’s UK’s 2025 audit, 4 in 10 people said they did not feel they were given enough information about Parkinson’s when they were diagnosed. 1 in 4 people taking these medications also had no recorded discussion about behavioural side effects in the last year.
Siôn says many people report being “caught completely off guard” when these behaviours started and “didn’t realise they were a possibility”.
In 2017, NICE guidance stated that people taking these medicines, and their families, should receive both verbal and written information about these risks and should be regularly monitored.
This does not mean health professionals or information providers are failing to discuss side effects altogether. It shows how difficult it can be to communicate risk clearly and help people recognise problems early, particularly when side effects affect behaviour, judgement or insight.
Supporting people earlier
Parkinson’s UK urges anyone experiencing behavioural side effects to speak to a specialist or Parkinson’s nurse as early as possible. Changes to medication or dosage can often help reduce the impact of these side effects. The charity also offers practical guidance and support for people living with Parkinson’s and their families, including a free confidential helpline.
This shows the importance of creating clear, accessible medicines information. That includes using plain language, explaining behavioural side effects clearly, involving families and carers where appropriate and making sure people know what warning signs to look out for over time.
Parkinson’s UK says conversations about behavioural side effects should become a more routine part of appointments and medicines discussions.
For organisations producing health information, this raises questions about medicines information across different conditions and treatments.
On 19 June, PIF will be bringing together partners from across charities, healthcare and industry to continue this conversation and explore how we can support each other to improve medicines information for patients and families.
We would also be interested in hearing from organisations about medicines information challenges in their own areas of work, and examples of approaches which have helped improve understanding, accessibility or earlier recognition of side effects.
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References:
https://healthinnovation-kss.com/wp-content/uploads/2023/03/State-of-the-Nation-Report-FINAL.pdf
National Institute for Health and Care Excellence (NICE). Parkinson’s disease in adults: recommendations. NG71. 2017. Available at: https://www.nice.org.uk/guidance/ng71/chapter/Recommendations