Research Article Effects of Paliperidone Palmitate on Coagulation: An Experimental Study Enver Demirel YJlmaz, 1 Sedat Motor, 2 Fatih Sefil, 3 Neslihan PJnar, 4 Hanifi Kokacya, 5 Mustafa Kisa, 6 and Suleyman Oktar 6 1 Department of Psychiatry, Faculty of Medicine, Bezmialem University, Istanbul, Turkey 2 Department of Biochemistry, Faculty of Medicine, Mustafa Kemal University, Hatay, Turkey 3 Department of Physiology, Faculty of Medicine, Mustafa Kemal University, Hatay, Turkey 4 Department of Pharmacology, Faculty of Medicine, Mustafa Kemal University, Hatay, Turkey 5 Department of Psychiatry, Faculty of Medicine, Mustafa Kemal University, Hatay, Turkey 6 Department of Pharmacology, Faculty of Medicine, Mevlana University, Konya, Turkey Correspondence should be addressed to Suleyman Oktar; suleymanoktar@yahoo.com Received 24 September 2013; Accepted 8 December 2013; Published 9 February 2014 Academic Editors: J. Csernansky and E. Ruther Copyright © 2014 Enver Demirel Yılmaz et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objective. Te aim of the present study was to examine the efects of a new antipsychotic drug paliperidone palmitate on hemogram and coagulation parameters in rats. Materials and Methods. Experiments were performed on 22 female albino Wistar rats (8–12 weeks old). Control group was given drinking water as vehicle (0.3mL). PAL-1 rats were given 1mg/kg paliperidone palmitate (in 0.3mL drinking water) by oral gavage once a day for ten days and PAL-3 rats received 3mg/kg paliperidone palmitate (in 0.3mL drinking water) by oral gavage for ten days. Blood samples were drawn from the heart 24 hours afer the last drug dose, and hemogram and coagulation parameters were measured with automated analyzers. Results. Hemogram did not change in the paliperidone treated groups compared to the controls. Factor VIII levels decreased in the PAL-1 and PAL-3 groups; and this decrease was signifcantly greater in the PAL-3. Factor IX levels decreased in PAL-3 rats, but its levels also increased in PAL-1 rats compared to the control. Discussion. Paliperidone has led to changes in the serum levels of coagulation factors VIII and IX in rats. As a result, paliperidone may be causing thromboembolism or bleeding in a dose-independent manner. 1. Introduction Several studies showed the relationship between venous thromboembolism and the use of antipsychotic drugs espe- cially atypical agents [1]. Many clinical studies have pointed to thrombogenic potential of atypical antipsychotic compounds such as clozapine, risperidone, and olanzapine. Cerebrovas- cular adverse events such as stroke and transient ischemic attack were observed at a high rate in some clinical trials in patients who received treatment with olanzapine or risperi- done [2]. For example, the incidence of cerebrovascular adverse events related to risperidone in elderly patients was 3.8%, compared with 1.5% placebo [3]. In a previous study, the relationship between antipsychotic medications and treat- ment of venous thromboembolism was strongly supported by a large, nested case-control study [4]. Although several hypotheses have been proposed, the biological mechanism explaining this relationship is unknown. Drug-induced seda- tion, obesity, hyperleptinemia, antiphospholipid antibodies, and increased activity of the hemostatic system may be high risk for thromboembolism [5]. Paliperidone (INVEGA, Ortho-McNeil-Janssen Pharma- ceuticals, Inc., Titusville, NJ, USA) was approved by the FDA for the treatment of schizophrenia in 2006. Paliperidone palmitate, a long-acting atypical antipsychotic drug, is used for adults for the treatment of schizophrenia. Paliperidone is the 9-OH metabolite of risperidone and paliperidone palmi- tate is also the palmitate ester of paliperidone. Paliperidone palmitate belongs to the chemical class of benzisoxazole derivatives [6]. Te precise mechanism of paliperidone is Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 964380, 5 pages http://dx.doi.org/10.1155/2014/964380