New Atypical Antipsychotic Drug Brexpiprazole Improves Depression When Added to Antidepressants
Two studies published in the Journal of Clinical Psychiatry in 2015 suggest that the new atypical antipsychotic brexpiprazole (trade name Rexulti) safely improves depression when added to antidepressant treatment. The 6-week studies, both by Michael E. Thase and colleagues, compared brexpiprazole to placebo in people who had not responded adequately to one to three antidepressants and were taking at least one antidepressant at the time of the study.
The studies examined the effectiveness of different doses of brexpiprazole. Doses of 2mg/day and 3mg/day were more effective than placebo, while a dose of 1mg/day was not. The drug was well-tolerated by patients at each of these doses, although those taking the 3mg/day reported more side effects than those taking 2mg/day. The side effects included restless legs, weight gain, and headaches.
Like the atypical antipsychotic aripiprazole (Abilify), brexpiprazole partially blocks and partially stimulates dopamine receptors. While aripiprazole allows 61% activity at dopamine D2 receptors, brexpiprazole allows 43%. It is not yet clear how the new drug’s effects may differ from those of aripiprazole.
Another relatively new atypical antipsychotic drug, cariprazine (Vraylar) is approved by the Food and Drug Administration for schizophrenia and mania, but not yet for bipolar depression or as an add-on treatment to antidepressants in unipolar depression, although there are placebo-controlled trials showing that cariprazine can also treat these conditions.
Like aripiprazole and brexpiprazole, cariprazine also partially blocks and partially stimulates dopamine receptors. Unlike them, cariprazine is more potent at dopamine D3 receptors, which are linked to mood, motivation, and drug reward, than at D2 receptors, which are linked to motor control. It is not yet clear how these differences may change treatment outcomes or side effects.
