Haloperidol
plasma levels, and possibly
clozapine levels, are roughly halved by
phenobarbital. Aripiprazole,
chlorpromazine and possibly thioridazine levels are also reduced by
phenobarbital. The
plasma levels of quetiapine are predicted to be reduced by barbiturates.
Monitor concurrent use to ensure that the
antipsychotics remain effective. The manufacturers of
aripiprazole suggest doubling its dose. It is also important to consider the seizure potential when prescribing antipsychotic medications.