9-OH risperidone response in risperidone poor responders: An open study of drug response concordance

A major topic about the pharmacotherapy of schizophrenia is the wide variability of antipsychotic effects among patients when treated with each drug, leading to the clinical judgement of a limited 'class effect', also for similar molecules. Paliperidone is the major metabolite of risperidone and pharmacodynamic activities are highly comparable, even though some differences have been reported. Paliperidone showed to be effective in the treatment of schizophrenia in a number of short and long term studies, however only two short term studies evaluated the differences in clinical response among patients switched from risperidone to paliperidone. The aim of this study is to evaluate, by means of a naturalistic observational follow-up, the possible concordance of clinical response to risperidone and paliperidone. Thirty-one patients affected by schizophrenia treated with risperidone and showing poor clinical response were enrolled in the study. Patients were switched to paliperidone and assessed for psychopathology, cognition, general functioning, extrapyramidal tolerability and attitude towards treatment at baseline and after 2, 6 and 12 weeks of treatment. The repeated measures analysis showed an overall significant improvement on several domains after 12 weeks of treatment (Table 1). Remarkably over 40% of patients showed a non-concordant clinical response to paliperidone and risperidone. In conclusion, this naturalistic observation suggests that paliperidone and his mother drug, risperidone may show significant differences both in efficacy and tolerability at individual level. Reasons for this should be looked for at biological levels not necessarily involving the receptor affinity and pharmacological activity profile. © 2012 Elsevier GmbH. All rights reserved.