Effect of olanzapine treatment on INR of a patient receiving warfarin therapy

Olanzapine is an atypical antipsychotic drug, commonly used in the management of psychotic symptoms in patients with schizoprenia and bipolar affective disorder. Deep venous thrombosis is a manifestation of venous thromboembolism. It is very well known that use of antipsychotic drugs increase the risk of thrombosis in a patient with schizophrenia. It has been reported in many studies the effects of olanzapine on thrombosis but there isn’t any report about the effect of olanzapine on international normalized ratio (INR). in the medical literature. In this paper, a patient with schizophrenia and also family history of deep venous thrombosis who emerged deep venous thrombosis after being started on olanzapine treatment and effect of olanzapine treatment on INR has been reported.