The interactions between antipsychotic drugs and antiepileptic drugs have been even less studied than the antidepressants. Some psychotropics, such as haloperi-dol, mainly metabolize using the P450 system, others such as chlorpromazine use different liver mechanisms. However, decreases in the levels of some neuroleptics can occur in patients prescribed anticonvulsant drugs, and several studies have been carried out in patients with schizophrenia who have received both carbamaz-epine and a neuroleptic. Haloperidol levels can drop by up to 50% following coadministration of the antiepileptic (Arana et al., 1986). Clozapine and olanzapine primarily use the CYP1A2 isoenzyme, which may lead to interactions with some of the tricyclic antidepressants, and carbamazepine.
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