Dopamine agonists

How do they work?

Dopamine agonists (e.g., ropinirole, cabergoline, bromocriptine, pergolide, pramipexole, rotigotine) imitate the action of dopamine in the brain. The brain cells respond as if more dopamine were present (see Figure, below).

There are several types of dopamine agonist, and they each work in a slightly different way.

What are the benefits?

Dopamine agonists are useful in the early stages of Parkinson’s disease (PD), and may be used as a first treatment. Eventually, levodopa is usually required, and dopamine agonists can be given with levodopa, allowing a lower dose of levodopa to be used.

Long-term treatment with dopamine agonists tends to cause fewer dyskinesias and ON–OFF fluctuations than levodopa, and tends to be preferred in younger people with PD. However, there is no strong evidence that starting treatment with a dopamine agonist is preferable to starting treatment with levodopa.

What are the side effects?

Dopamine agonists can sometimes cause nausea, vomiting, low blood pressure on standing, confusion and hallucinations, constipation, abnormal dreams, and fatigue. However, some of these can be reduced by gradual introduction of the medication, or by reduction of the dose. The rotigotine patch can also cause skin reactions at the patch application site, e.g., rash or itchiness.

Because of the way they work, different dopamine agonists tend to be associated with different side effects.

The rotigotine patch

Rotigotine has been developed as an adhesive skin patch that is replaced every 24 hours, with the medication being absorbed into the body through the skin. The patches are available in several doses (more than one patch may be necessary to achieve the appropriate dose), and may be a practical alternative to oral tablets for some people with PD – although the patches must be stored in a refrigerator prior to use.

Ropinirole XL/CR

A slow-release form of ropinirole has been developed, which allows a more convenient once-daily dosing schedule. This is known as ropinirole XL or ropinirole CR.

How oral dopamine agonists work

(Click on animation to enlarge.)