Fluoxetine and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)

Objective: To report three new cases of the fluoxetine-induced syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Clinical picture: All three cases occurred in elderly psychiatric inpatients treated for depression with standard doses of fluoxetine within one month of starting the medication. All three patients were clinically symptomatic of SIADH. Treatment: In all three patients the medication was ceased and fluid restriction commenced. One patient required intravenous saline. Outcome: All three patients recovered fully within three weeks, None were rechallenged. Conclusions: The symptoms of hyponatraemia due to fluoxetine-induced SIADH may be difficult to distinguish from the symptoms of depression, unless appropriate laboratory investigations are made.