Effects of venlafaxine treatment on clozapine plasma levels in schizophrenic patients.

Depressive symptoms are found at any stage of schizophrenia, and antidepressant medication may be beneficial. Selective serotonin reuptake inhibitor antidepressants have been considered safe in schizophrenia but in combination with clozapine, that is widely used in chronic treatment-resistant schizophrenia, remarkable pharmacokinetic interactions can occur causing an elevation in clozapine plasma levels. To investigate this further, the plasma levels of clozapine were measured in 11 schizophrenic male patients with depressive symptoms who were administered both clozapine and venlafaxine.