High-dose olanzapine and prolactin levels

Background: This study evaluates whether high-dose olanzapine is associated with elevation of serum prolactin levels. Method: Twenty-four patients taking daily doses of olanzapine of 20, 25, 30, and 40 mg for DSM-IV schizophrenia or schizoaffective disorder had serum prolactin levels measured. The patients were all from one author's (J.L.K.'s) clinical practice. The mean duration of olanzapine therapy was 15.3 months at a dose of at least 20 mg/day. Data were gathered in 2000 and 2001. Results: There was no significant correlation between olanzapine dose and prolactin level (Pearson product moment correlation coefficient = 0.09). No significant differences were found between mean prolactin values in each dose group. Conclusion: There was no significant elevation of prolactin with higher doses of olanzapine. Thus, preliminary evidence suggests that using higher doses of olanzapine is generally safe with regard to prolactin levels.