The Role of Dopamine Agonists in Parkinson’s Treatment
What are dopamine receptor agonists?
These medicines constitute a class of drugs used to treat Parkinson’s disease (PD) symptoms that mimic the action of naturally occurring dopamine. Although this class of medication is less potent than levodopa, they can be very beneficial in treating symptoms for long periods of time.
What are the currently available dopamine receptor agonists in the United States?
Four dopamine agonists are now Federal Drug Administration (FDA) approved and available for use in the United States to treat PD: Mirapex® (pramipexole), Requip® (ropinirole), Neupro® (rotigotine) and Apokyn® (apomorphine). Pramipexole and ropinirole are available in both regular and long acting formulations. Rotigotine is available in a patch form, placed on the skin once daily. Apomorphine is delivered by injection and thought of as a “rescue” medication, with onset of action within 10 minutes. It is also under FDA review in the form of a sublingual film, also to be used as a “rescue” medication.
Where do the dopamine receptor agonists fit in the overall strategy for optimizing the treatment of Parkinson’s disease?
Dopamine agonists can be used as monotherapy, or as the only drug taken for PD. In addition, they can be used as adjunctive or “add on” medications to supplement the use of levodopa when further dopaminergic effect is desired or when complications of levodopa treatment, such as dyskinesias, “wearing off,” and motor fluctuations, are encountered.
What are some possible side effects of the dopamine receptor agonists?
Dopamine agonists have many of the side effects of other dopaminergic agents. These include hallucinations and orthostatic hypotension (drops in blood pressure with standing). Leg swelling can also occur. Dopamine agonists can induce sleepiness as well as sleep attacks (falling asleep without warning) and must be used with great caution in those patients who are driving. Compulsive behavior is a well described side effect and could take the form of over-shopping, over-eating, gambling or hyper-sexuality.
In some patients, a withdrawal syndrome can be experienced as the dopamine agonist is lowered and stopped. Symptoms of the withdrawal syndrome can include anxiety, pain, depression, and even suicidality. Patients should be warned about the possibility of experiencing withdrawal when a dopamine agonist is tapered so if they experience these symptoms, they can modify how the medication is weaned off.