Treatment-resistant schizophrenic patients respond to clozapine after olanzapine non-response

Background: Treatment-resistance in schizophrenia remains a public health p roblem. Clozapine has been shown to be effective in about one third of this population, but carries with it medical risks and weekly blood draws. As o lanzapine is a drug with a very similar biochemical profile to clozapine, i t is important to evaluate whether non-response to olanzapine predicts cloz apine non-response. Methods: Forty-four treatment-resistant patients received eight weeks of ol anzapine, either in a double-blind trial or subsequent open treatment at a mean daily dose of 25 mg/day. Two of 44 patients (5%) responded to olanzapi ne treatment. Patients who did not respond could then receive clozapine. Tw enty-seven subsequently received an 8-week open trial of clozapine. Results: Patients who did and did not receive clozapine did not differ demo graphically or in psychopathology. Eleven of 27 (41%) met a priori response criteria during clozapine treatment (mean dose 693 mg/day) after failing t o respond to olanzapine. Conclusions: This study demonstrates that failure to respond to olanzapine treatment does not predict failure to clozapine. Treatment-resistant patien ts who fail on olanzapine may benefit from a subsequent trial of clozapine. (C) 1999 Society of Biological Psychiatry.