Physicians use dopamine agonists to treat medical conditions that result from a permanent or temporary need for more dopamine in the body. This situation includes Parkinson’s disease, restless leg syndrome and an overactive pituitary gland. According to Medline Plus, bromocriptine and ropinirole are two examples of dopamine agonists. While these drugs act in place of dopamine to restore function, they also may cause side effects.
Nausea and Vomiting
Too much dopamine agonist in the blood stimulates the brain’s vomiting center, resulting in nausea and vomiting, say Dr. William Weiner and colleagues in their book “Parkinson’s Disease: A Complete Guide for Patients and Families.” To avoid this situation, a physician will prescribe a low initial dose of a dopamine agonist and gradually increase the dosage over time.
Drowsiness
Tiredness and sudden onset of sleep during daily activities can occur with the use of dopamine agonists. In some cases this occurs without warning and is therefore potentially dangerous. GlaxoSmithKline, manufacturer of ropinirole under the name Requip, recommends that doctors warn patients taking dopamine agonists about this side effect and caution them not to drive or operate machinery if it occurs. The alternative is to stop taking the drug.
Cardiac Problems
Dopamine agonists can cause blood-pressure-related side effects such as low blood pressure and fainting when standing up from a seated position. They may also cause changes in the valves and muscles of the heart, a more common side effect with bromocriptine than ropinirole, according to a review by Dr. Frank Andersohn of the University of Bremen, and Dr. Edeltraut Garbe of the Charite Universitaetsmedizin in Berlin.
Hallucinations
According to Dr. Weiner and colleagues, patients taking dopamine agonists have reported psychiatric problems such as hallucinations, confusion, delusions and psychosis. Lowering the dose the patient receives can reduce this side effect, although this may also decrease the beneficial effects of the drug.
Pathological Addiction
A small but significant number of patients taking dopamine agonists have reported that they developed an extreme addiction to activities such as gambling, shopping or sex. This is most common in men taking dopamine agonists who developed Parkinson’s disease at a younger age than is normal, according to a study report by Dr. William Stamey and Dr. Joseph Jankovic of the Baylor College of Medicine in the March 2008 issue of "The Neurologist." It is also possible to become addicted to dopamine agonists themselves as side effects can include euphoria and increased sexual function.
References
- Medline Plus: Bromocriptine
- Medline Plus: Ropinirole
- “Parkinson’s Disease: A Complete Guide for Patients and Families," 2nd ed.; William J.Weiner, Lisa M.Shulman, and Anthony E. Lang; 2007
- U.S. Food and Drug Administration: Requip; GlaxoSmithKline Prescribing Information
- “Movement Disorders”; Cardiac and Noncardiac Fibrotic Reactions Caused by Ergot-and Nonergot-Derived Dopamine Agonists; Frank Andersohn and Edeltraut Garbe; January 2008
