Antidepressants can induce SIADH and it can be a serious complication. It is frecuently asociated with SSRIs (Selective Serotonin Reuptake Inhibitors) but this syndrome can be caused by another antidepressants, drugs and another causes can be involved.

We report the clinical course of an antidepressants induced SIADH with SSRIs and Mirtazapine and propose psychopharmacologic alternatives.

We describe the case of a 25 years old man, hypertensive in treatment with thiazides, polytraumatized as a result of a suicide attempt. The patient was treated with Sertraline and a SIADH occurred. Stopped Sertraline and diuretics and then, the patient was treated with Mirtazapine and Bisoprolol but hyponatremia was persistent. Then we use Trazodone and the sodium levels were normalized.

Hyponatremia is a potentially dangerous side effect of antidepressants and is not exclusive to SSRIs. Current evidence suggests a relatively higher risk of hyponatremia with SSRIs and venlafaxine, especially when combined with patient risk factors. In our case, the risk was increased by the polytrauma and thiazide diuretics. Although, according to the literature, the risk associated with mirtazapine is moderate, in our case, hyponatremia was persistent and sodium levels were normalized when stopped Mirtazapine and started Trazodone.

We have to take into account risk factors associated with SIADH and modify them as far as possible. Trazodone could be an alternative treatment for patients with SIADH.