Dopamine agonist drugs

This leaflet concerns a category of drugs used to treat Parkinson's disease (PD) and sometimes Restless Legs Syndrome (RLS).

These drugs are known as dopamine agonists. In PD there is a reduction of a chemical (dopamine); this is because the illness affects brain cells that produce dopamine. The function of dopamine in the brain is signalling between cells in the movement circuits of the nervous system. Many of the symptoms of PD arise because of a reduction of brain dopamine levels. RLS is also affected by dopamine levels in the brain.

Dopamine agonists are drugs which act in the brain like dopamine. Chemically dopamine agonists are very similar to dopamine and are an important way of making up for the reduction of brain dopamine levels in PD or RLS.

These drugs can be used alone in early PD or in combination with other drugs in patients who have had the condition for longer.

Dopamine agonist drugs are usually very effective in dealing with the main symptoms of Parkinson's disease (tremor, slowness and stiffness) or RLS. They do not suit every patient and your neurologist will assess your response to the drug at outpatient clinic visits. If the drug is not suiting you it can be reduced or discontinued. Sometimes dopamine agonists are not very effective. If this is the case then your neurologist will adjust the dosage or change your medication to something different.

Dopamine agonists can be given in tablet form (Ropinirole, Pramipexole), a skin patch (Rotigotine) or- in PD- by injection (Apomorphine).

Side Effects

Dopamine agonists are usually safe and effective. However side effects can sometimes occur. It is very important that you are aware of these.

• Some patients develop excessive daytime drowsiness and a tendency to fall asleep suddenly. If this happens it may be necessary to reduce or discontinue the drug. You should contact your neurologist or Parkinson's disease nurse for advice if this happens. It is very important that you cease driving immediately if you develop this side effect as road accidents can occur as a result of this side effect.
• Some patients develop nausea and vomiting. Sometimes, an antidote to this (Domperidone) is prescribed with the dopamine agonist for a week while you are getting used to the drug. After that you should not need the Domperidone. Occasionally however the nausea does not settle. If you develop this problem despite having used Domperidone you should ask your GP or Parkinson's disease nurse for advice.
• Occasionally patients develop mental confusion, hallucinations or both. This is more likely to occur in older patients but not always. Again it is usually necessary to reduce or discontinue the drug if this happens and you should request advice from your GP, Parkinson's nurse or consultant if this occurs.
• Some patients (15-20%) can develop an altered form of behaviour known as "impulse control disorder". This usually takes the form of obsessive behaviour leading to problems such as excessive gambling, spending too much money and buying things you do not need, excessive eating or increased sexual feelings or sexual behaviour.
• Some other patients become obsessional about collecting things in a way they did not do so previously. Other behaviours that can develop include obsessional eating, drawing, painting or other activities. If you develop any of these symptoms of impulse control disorder please contact your consultant or Parkinson's disease nurse urgently for advice as it is very likely the drug will need to be discontinued.
• Other side effects sometimes occur. Some patients develop swollen ankles and you should mention this at your next clinic visit if it occurs. Patients on Apomorphine can develop skin problems at the site of injections - the Parkinson's disease nurse can usually advise about this. Patients using Rotigotine patches can develop skin irritation at the site of the patches. Again the neurology clinic or Parkinson's disease nurse can usually advise about this.

If you have any concerns about your medication you should discuss this with your GP, Parkinson's disease nurse or consultant. RLS patients will not have a PD nurse and so should seek advice from their GP or neurologist.