Deep venous thrombosis (DVT) is a rare but potentially life-threatening adverse effect of antipsychotic medication. In this paper, we present a case of DVT that occurred during the first month of risperidone use. The patient Mr. M., aged 33, presented with a delusion of persecution based on a purely interpretative mechanism.

The diagnosis of a delusional disorder of the persecution type was made and the patient was started on risperidone 2mg bid. Two weeks later, the patient was admitted to the internal medicine department for femoro-iliac DVT.

Etiological investigation ruled out common congenital as well as acquired causes for thrombophilia, and DVT was hence attributed to risperidone use. The patient quickly responded to heparin then warfarin treatment. Risperidone was switched to amisulpride.

Although antipsychotics have been widely used for more than fifty years, their association with DVT has not been discovered until recently.

DVT usually occurs during the first three months of antipsychotic use and is more common with atypical and low-potency typical drugs than with high-potency conventional antipsychotics. Amisulpride appears to be the antipsychotic drug least associated with DVT.

This case highlights a scarce yet serious side effect associated with antipsychotic use. Caution should be applied when initiating such a treatment in patients with a high risk of thrombosis. Occurrence of DVT in a patient on antipsychotic medication should lead to the current treatment being stopped, and if necessary, switched to either amisulpride or a highpotency conventional drug.