Dopamine agonists and antipsychotics.

There can potentially be a number of clinical interactions that could adversely affect patient outcomes in a patient with a prolactinoma and psychiatric disease that might require antipsychotic and dopamine agonist treatment. Dopamine agonists stimulate the dopamine D2 receptor, resulting in a decrease in prolactin (PRL) levels and in prolactinoma size but action on dopamine receptors in the meso-limbic system may rarely cause psychosis and more commonly cause impulse control disorders. The psychiatric benefits of antipsychotic agents involve blocking the D2 and other dopamine receptors but this blockade often also causes hyperprolactinemia. In patients with macroprolactinomas and psychosis, observation, estrogen/progestin replacement, and surgery can be considered in addition to dopamine agonists. In those who require dopamine agonists for PRL and tumor size control, the introduction of antipsychotics may blunt this effect, so that higher doses of the dopamine agonists may be needed. Alternatively, antipsychotics that have less of a blocking effect at the D2 receptor, such as aripiprazole, can be tried, if appropriate. For patients already on antipsychotic drugs who are found to have a macroprolactinoma for which dopamine agonists are required, dopamine agonists can be initiated at low dose and the dose escalated slowly. However, such patients require careful monitoring of psychiatric status to avoid the rare complication of exacerbation of the underlying psychosis. Again, if appropriate, use of antipsychotics that have less of a blocking effect at the D2 receptor may allow lower doses of dopamine agonists to be used in this situation.