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Parkinson's Disease: Dopamine Agonists

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An agonist is a drug that is capable of binding to a receptor on a cell and causing the same reaction usually produced by a naturally occurring substance, i.e. they mimic its action. In this way, dopamine agonists bind to dopamine receptors and produce similar effects to the dopamine naturally found within the brain.

A number of clinical trials have compared the effects of dopamine agonists with levodopa in patients with early Parkinson’s disease. They show that treatment with levodopa gives greater improvement in rigidity, tremor and bradykinesia and maintains movement for longer than dopamine agonists.

However, dopamine agonists are less likely to produce complications than levodopa, such as ‘end of dose wearing off’ and ‘on-off-dose phenomenon’.

Currently, there are a variety of dopamine agonists available, most of them as multiple dose tablets, but also as once-daily transdermal patches.

Advantages and disadvantages of the dopamine agonists

Advantages	Disadvantages
Associated with fewer motor complications than levodopa	Effects on motor symptoms not as great with levodopa
Avoids the need for levodopa in early Parkinson’s disease	Multiple daily doses often needed (usually 3 doses daily)
Less frequently administered than levodopa formulations	Side effects including sleep disturbances, hallucinations, dizziness, gastrointestinal upset

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Glossary

Glossary entries within this article:

Action tremor
- Involuntary movement of limbs that occurs when limbs are moved voluntarily.
Adjunctive treatment
- Additional or auxiliary treatment to primary drug.
Agonist
- Chemical substance or drug that enhances or mimics the activity of a neurotransmitter, for example dopamine.
Amantadine
- Chemical substance used in the treatment of Parkinson’s disease to improve tremor, rigidity and bradykinesia.
Antagonist
- Chemical substance or drug that reduces the activity of a neurotransmitter, for example dopamine.
Dopamine
- Neurotransmitter in the CNS. Dopamine deficiency is one of the major anomalies in Parkinson’s disease leading to the major symptoms such as bradykinesia, tremor, and rigidity.
Dyskinesia
- Abnormal involuntary body movement that is a common side effect after long-term intermittent receptor stimulation in the brain e.g. pulsatile l-dopa treatment. It results in jerking, twisting and abnormal turning.
Levodopa
- Precursor that is metabolized to dopamine in the brain. It is in important drug in treatment of Parkinson’s disease.
Rigidity
- An abnormal stiffness of the muscles. The reflexes necessary for balance become impaired. The risk of falling increases.
Tremor
- An uncontrollable shaking, in particular the hands. Performing everyday tasks, such as fastening buttons or shaving, becomes more difficult.

In the glossary you will find terms that we have provided with some extra-information.

glossary

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