PO94 | The use of antidepressant drugs and benzodiazepine hypnotics as an unusual risk factor for VTE

Background: Venous thromboembolism (VTE) involving the inferior vena cava (IVC) is a rare but life-threatening condition. Antidepressant drugs and benzodiazepine hypnotics have sedative effects that cause reduced activity in the patient and may increase the risk of VTE. We report a case of massive IVC thrombosis in a patient with major depressive disorder on long-term pharmacological treatment. Case Report: A 69-year-old celiac woman with a history of major depression (diagnosed in 2020), arterial hypertension, dyslipidemia and hypothyroidism was admitted in October 2024 for the presence of acute-onset bilateral swelling and pain in the lower limbs. The patient was on chronic treatment with duloxetine, valproic acid, lormetazepam and pregabalin. In a previous hospitalization, a right parathyroid incidentaloma (7 mm) was found, and subsequently in periodic follow-up. Imaging studies (TC scan and ultrasonography of the abdomen and lower limbs) revealed an extensive thrombosis of the IVC, sparing the supra-hepatic segment, with bilateral iliac and femoral vein involvement, extending to the popliteal veins on the right side. Initial dilation of the abdominal aorta (42 mm) was also evidenced. The episode of VTE was apparently unprovoked, because of the absence of known thrombotic provoking factors. Antiphospholipid syndrome or other autoimmune systemic disorders and active cancer were excluded. However, a hereditary protein S deficiency was diagnosed, and confirmed with repeated evaluations (ranging from 40 to 43%). The patient was treated with a low molecular weight heparin (enoxaparin 100 IU /kg of body weight, every 12 hours), and then apixaban, 5 mg twice daily, was started. The patient’s psychiatric status improved during the hospitalization, under continued psychiatric support. Follow-up imaging with lower limb ultrasonography after two weeks showed a complete recanalization of the femoral veins. Conclusions: This case underscores the importance of the evaluation of patient’s existing VTE risk factors (e.g. thrombophilic conditions, hypothyroidism, obesity) during the treatments with antidepressant drugs and benzodiazepine hypnotics. The sedative effects of these drugs may be associated to the development of VTE in predisposed patients.