MON-054 Aripiprazole Use as a Cause for Dopamine Agonist Failure in the Treatment of Prolactinomas

Abstract Disclosure: E. Mignone: None. A. Jukes: None. V. Rowan: None. R. Allison: None. S.M. De Sousa: None. Prolactinomas are the most common hypersecretory pituitary adenoma. Traditional first line therapy is dopamine agonists, which are highly effective and tolerated in the majority of cases. However, dopamine agonists have the potential for psychiatric complications such as psychosis, impulse control disorders and anxiety/depression. It has been repeatedly suggested that aripiprazole may be considered in individuals with a psychiatric disorder and prolactinoma, potentially enabling dopamine agonist dose reduction or even cessation. We report the first case of aripiprazole competing with cabergoline and reducing its efficacy in the treatment of a giant prolactinoma, as evidenced by an immediate and marked rise in serum prolactin (approx. 350% increase over 5 weeks) despite stable cabergoline dosing. We also present a systematic review of aripiprazole use in prolactinomas, showing that aripiprazole monotherapy effectively reduces serum prolactin and that concurrently commenced aripiprazole/dopamine agonist dual therapy may still permit prolactin lowering, although there were no previous cases where aripiprazole was added to established dopamine agonist therapy to indicate the direct effect of aripiprazole on dopamine agonist efficacy. The case presented herein is the first case to our knowledge to illustrate the effect of adding aripiprazole to existing DA therapy, finding clear prolactin excursion following aripiprazole commencement despite stable cabergoline dosing. This example of aripiprazole-induced DA treatment failure is an important caveat to the suggested use of aripiprazole in the latest prolactinoma guidelines. Specifically, we caution against the addition of aripiprazole to DA therapy where timely prolactinoma treatment is essential - for example, individuals with aggressive prolactinomas or those presenting with visual defects. In addition, all patients on dual aripiprazole and DA therapy for prolactinomas should be closely monitored, especially if there are risk factors for tumour aggressiveness. Presentation: Monday, July 14, 2025