Clozapine,
haloperidol and
risperidone plasma levels can be roughly halved by
carbamazepine. Aripiprazole, bromperidol, fluphenazine,
olanzapine, quetiapine, sertindole, and tiotixene levels are also reduced by
carbamazepine. An increase in the
serum levels of
carbamazepine or its epoxide
metabolite (which is thought to cause some of the adverse effects of carbamazepine) has been reported in patients given loxapine,
haloperidol, quetiapine,
risperidone, or
chlorpromazine with
amoxapine.
Toxicity has occurred. Isolated cases of Stevens-Johnson
syndrome and the neuroleptic malignant
syndrome have occurred in patients taking
antipsychotics with
carbamazepine.
Monitor
carbamazepine levels if loxapine,
haloperidol, quetiapine,
risperidone, or
chlorpromazine are given. Also monitor concurrent use to ensure that the
antipsychotics remain effective, (especially
risperidone,
clozapine and haloper- idol). The manufacturers recommend using double the dose of
aripiprazole in patients taking
carbamazepine. The risk of Stevens-Johnson
syndrome seems to be highest during the first 2 weeks of treatment and appears to be mostly confined to the first 8 weeks of treatment. Also note that the combination of
clozapine and
carbamazepine is predicted to increase agranulocytosis and one case of fatal
pancytopenia has been reported. It is also important to consider the seizure potential when prescribing antipsychotic medications.