Brexpiprazole (Rexulti)
A medicine for schizophrenia, for depression alongside an antidepressant, and for agitation in Alzheimer's dementia. People whose CYP2D6 enzyme barely works are told to take half the usual dose.
What this drug connects to
The genes involved
Brexpiprazole (Rexulti), a close relative of aripiprazole, is cleared partly by CYP2D6. For people whose CYP2D6 barely works, poor metabolisers, its US label says to take half of the recommended dose, and a quarter if they also take a medicine that strongly or moderately blocks CYP3A4, the other enzyme that clears it. The label does not ask for a test; the change is for people already known to be poor metabolisers.
US prescribing information for REXULTI (brexpiprazole), revised April 2026, section 2.7, Dosage Modifications for CYP2D6 Poor Metabolizers. This is the label itself, not a CPIC guideline.
Questions about Brexpiprazole (Rexulti)
What is brexpiprazole?
Brexpiprazole, sold as Rexulti, is an antipsychotic medicine. In the US it is used for schizophrenia in adults and teenagers from 13, added to an antidepressant for major depression in adults, and for agitation in people with dementia due to Alzheimer's disease. It is a close relative of aripiprazole.
What does CYP2D6 have to do with it?
CYP2D6 is one of the two liver enzymes that clear brexpiprazole. Some people are born with two copies of CYP2D6 that barely work, called poor metabolisers, and in them the medicine stays in the body longer and reaches higher levels.
What does the label say for poor metabolisers?
Take half of the recommended dose. If a known poor metaboliser also takes a medicine that strongly or moderately blocks the other enzyme, CYP3A4, the label says to take a quarter of the recommended dose.
Do I need a gene test before taking it?
The label does not ask for one; its dose changes are for people known to be poor metabolisers. If you already have a pharmacogenomic result that says so, show it to your prescriber. Never change the dose of an antipsychotic on your own.
What are the boxed warnings on brexpiprazole?
Two. Older people with dementia-related psychosis treated with antipsychotics have a higher risk of death, and antidepressant treatment raises the risk of suicidal thoughts and behaviour in children, teenagers and young adults. Neither warning is about genes.
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Brexpiprazole (Rexulti). MyGeneLog™. https://www.mygenelog.com/drugs/brexpiprazole