Olanzapine: evaluation of the in vivo cytogenetic effect.

BACKGROUND/AIMS: Olanzapine (OLZ), an atypical antipsychotic, is licensed for use in the treatment of schizophrenia and other psychiatric disorders.

METHODS

OLZ cytogenetic effects were investigated by evaluating the frequency of Sister Chromatid Exchanges (SCEs) and Proliferation Rate Index (PRI) in cultured lymphocytes of schizophrenic patients who were under treatment of OLZ. SCE estimation is one of the most sensitive biomarkers of potential cytotoxicity, while PRI is used as a valuable marker of cytostatic activity.

RESULTS

Our results showed a statistically significant increase of SCEs in the cultured lymphocytes of patients (p < 0,001) compared to the lymphocytes of healthy donors, a statistically significant increase of SCEs (p < 0.001) in the lymphocytes of smoker patients compared to those of non-smoker patients and a statistically significant increase of SCEs (p < 0.001) in the lymphocytes of chronic recipients of OLZ compared to those of the patients with recent initiation of treatment. We did not detect any statistically significant differences with respect to PRI between the various groups examined.

CONCLUSIONS

Our results indicate a mild cytotoxic-but not cytostatic-effect of OLZ which was more prominent in smokers and in chronically treated patients. That effect should be taken into consideration by psychiatrists upon assessing the benefit/risk ratio of their prescriptions.