A dopamine antagonist is a chemical, medication or drug that prevents the actions stimulated by dopamine. Dopamine is a naturally produced chemical in the body that binds to regions in the brain to help regulate emotions and movement. Dopamine antagonists disrupt the activity of dopamine by blocking dopamine binding sites without activating them. These medications are used to treat a variety of disorders.
Common Dopamine Antagonists
Most dopamine antagonists are used as medications for psychiatric disorders such as schizophrenia, psychosis and sometimes depression. Haloperidol (Haldol), chlorpromazine and risperidone (Risperdal) are classic dopamine antagonists used to treat the symptoms of psychosis -- a mental state in which a person loses touch with reality. Olanzapine (Zyprexa) is a newer dopamine antagonist commonly prescribed for schizophrenia. Dopamine antagonists can also be used for less common health problems, such as Tourette syndrome. Metoclopramide (Reglan) is a dopamine antagonist that is approved for use to treat some cases of severe acid reflux, or gastroesophageal reflux disease, and slow stomach emptying caused by diabetic nerve damage.
Dopamine Antagonists and Psychiatric Conditions
It has been a long-standing theory that dopamine overactivity or oversensitivity plays a role in schizophrenia, psychosis and hallucinations. The dopamine antagonists used for psychosis and hallucinations are believed to work by specifically binding to the dopamine receptors located in an area near the front of the brain that is responsible for integrating emotions, perception of surroundings and self-control. When the dopamine antagonists bind to the receptors, they prevent dopamine from binding and thus from exerting excessive dopamine effects believed to contribute -- at least partially -- to symptoms.
Dopamine Antagonists and Mood
Dopamine antagonists are sometimes used with traditional antidepressants in the treatment of severe, persistent depression. For example, a prescription medication containing a combination of the dopamine antagonist olanzapine and the antidepressant fluoxetine (Symbyax) has been approved by the U.S. Food and Drug Administration for treatment-resistant depression and depressive episodes associated with bipolar disorder. If a doctor prescribes a dopamine antagonist for depression, this does not necessarily imply that the person is also suffering from hallucinations or psychotic symptoms.
Dopamine Antagonists in Tourette Syndrome
Tourette syndrome is a disorder in which people suffer from tics. These uncontrolled, quick, repetitive muscle movements can be extremely difficult to control, socially embarrassing and potentially physically limiting and painful. Few treatment options are available, and dopamine antagonists have provided some relief in some people for whom other forms of therapy have been ineffective. Pimozide (Orap) is the most commonly used dopamine antagonist for Tourette syndrome tics. A research article published in the January 2014 issue of "Clinical Neuropharmacology" reported that a new dopamine antagonist, ecopipam, also demonstrated effectiveness in a small study. As of the time of publication, ecopipam has not been approved by the FDA.
Dopamine Antagonists for Hiccups, Vomiting and Migraines
Extreme cases of hiccups, vomiting or migraine may respond to dopamine antagonist action. Examples of drugs used for these medical problems include prochlorperazine (Compazine) and chlorpromazine. Effects may result from dopamine receptors in the digestive system, although these symptoms often occur as a result of an injury or irritation of the vagus nerve, which controls functions of the heart, lungs and digestive system.
Common side effects of dopamine antagonist medications include stiff movements resembling Parkinson disease, tremors, tiredness and irregularities of the hormones of the reproductive system.