Strategies for switching from conventional antipsychotic drugs or risperidone to olanzapine.

Background: This study compared the efficacy and safety of 4 therapeutically relevant strategies for switching clinically stable patients from a conventional antipsychotic drug or risperidone to olanzapine.
Method: Two hundred nine outpatients with a DSM-IV diagnosis of schizophrenia or schizo-affective disorder who were clinically stable while being treated with a conventional antipsychotic drug or risperidone were openly randomly assigned to either abrupt or gradual discontinuation of their prior antipsychotic drug. Patients were further randomly assigned in a double-blind fashion to immediate olanzapine initiation (olanzapine, 10 mg q.d. for 3 weeks) or stepwise initiation (a sequence of 1 week each on placebo; olanzapine, 5 mg q.d.; and olanzapine, 10 mg q.d.). The efficacy of these 4 switching paradigms was assessed using the Clinical Global Impressions (CGI)-Improvement scale, Patient's Global Impressions (PGI)-Improvement scale, and Positive and Negative Syndrome Scale (PANSS). Safety assessments included ratings for extrapyramidal symptoms, cognitive impairment, adverse events, laboratory parameters, weight change, and vital signs.
Results: The paradigm of gradual antipsychotic drug discontinuation combined with an initial full dose of olanzapine, 10 mg/day, had the most favorable efficacy and tolerability profile overall. By week 3, the majority of completing patients on all 4 switching paradigms were either improved or clinically unchanged (> 90%). No clinically significant differences between switching paradigms were seen in laboratory values or vital signs.
Conclusion: In this study, switching clinically stable outpatients with a diagnosis of schizophrenia or schizoaffective disorder to olanzapine was most successful when a full therapeutic dose of olanzapine was immediately initiated while gradually discontinuing prior conventional antipsychotic drug or risperidone treatment. Overall, switching was achieved without increased vulnerability to relapse or to occurrence of clinically burdensome antipsychotic drug withdrawal symptoms in the majority of patients.