Venous thromboembolism (VTE) has been associated with the diagnosis of a psychiatric disease, as well as with the treatment with psychotropic drugs. Recent reports suggest an association between several atypical antipsychotics agents (eg. olanzapine) and an increased risk for VTE.

We prospectively analysed and consequently followed-up olanzapine users in a cohort of 138 consecutive patients under 60 years of age (male=72, mean age 45 years) suffering from objectively confirmed VTE over a three-year period (2004 - 2006). Data on known acquired or genetic risk factors for VTE were recorded for each patient.

Four Caucasian patients (one female, three males; mean age 49 years, range 37-55 years) with spontaneous VTE treated with olanzapine were registered. Two patients were obese. The hospitalization was extended in the female patient. We found coagulation abnormalities in all our subjects (elevated levels of factor VIII:C, mild hyperhomocysteinemia, FV Leiden and prothrombin gene G20210A mutations).

These cases indicate that VTE might be associated with the use of olanzapine, at least in the presence of several acquired or inherited risk factors such as immobilization, obesity and disorders of coagulation homeostasis including factor V Leiden, prothrombin gene G20210A mutations, high levels of factor VIII and hyperhomocysteinemia. Subjects treated with olanzapine should be monitored clinically for VTE. Interestingly, in three patients symptoms occurred in the first six months of olanzapine treatment.