Higher serum clozapine level is associated with increased antiphospholipid antibodies in schizophrenia patients

Objectives: This study was to evaluate the relationship between clozapine and aPL in schizophrenia patients. Methods: 163 Participants were evaluated: 37 unmedicated schizophrenia patients, 50 clozapine-treated schizophrenia patients and 76 age- and sex-matched healthy controls. A fasting blood sample was taken for serum aPL and serum clozapine level. Serum aPL were measured by ELISA technique and HPLC method was used for the determination of serum clozapine level. Results: The unmedicated schizophrenia patients showed higher IgG aCL level [mean +/- SD: 1.51 +/- 0.81 and 1.25 +/- 0.13 U, respectively (t = 2.77, df = 111, p < 0.01)] and IgM aCL level [mean +/- SD: 1.53 +/- 0.54. and 1.33 +/- 0.15 U, respectively (t = -2.98, df = 111, p < 0.01)] compared with the healthy controls. The comparison of the clozapine-treated schizophrenia patients and the healthy controls showed significant difference in IgG aCL level [mean +/- SD: 1.74 +/- 0.90 and 1.25 +/- 0.13 U, respectively (t = -4.77, df = 124, p < 0.01)] and IgM aCL level [mean +/- SD: 1.62 +/- 0.83 and 1.33 +/- 0.15 U, respectively (t = -4.35, df = 124, p < 0.01)]. In clozapine-treated schizophrenia patients, the results of Pearson correlation coefficients showed that there was a significant positive relationship between serum IgM aCL and serum clozapine level (r = 0.461, p < 0.01), and serum IgG aCL were significantly correlated with serum IgM aCL (r = 0.279, p < 0.05). Stepwise multiple regression analysis was performed with various characteristics, such as duration of medication, daily dose and serum clozapine level as candidate factors for serum aCL (IgG and IgM isotypes) in clozapine-treated schizophrenia patients. Only serum clozapine level was able to enter into the regression model of IgM aCL (Model R-2 = 0.212, p < 0.05). Conclusions: A higher serum clozapine level is associated with an increased aPL in schizophrenia patients. (C) 2008 Elsevier Ltd. All rights reserved.