Mirtazapine as an alternative for selective-serotonin-reuptake-inhibitor-induced syndrome of inappropriate secretion of antidiuretic hormone
Article first published online: 18 JAN 2012
© 2012 The Authors. Psychiatry and Clinical Neurosciences © 2012 Japanese Society of Psychiatry and Neurology
Psychiatry and Clinical Neurosciences
Volume 66, Issue 1, page 80, February 2012
How to Cite
Mogi, T., Yoshino, A., Ikemoto, G. and Nomura, S. (2012), Mirtazapine as an alternative for selective-serotonin-reuptake-inhibitor-induced syndrome of inappropriate secretion of antidiuretic hormone. Psychiatry and Clinical Neurosciences, 66: 80. doi: 10.1111/j.1440-1819.2011.02297.x
- Issue published online: 18 JAN 2012
- Article first published online: 18 JAN 2012
- Received 21 April 2011; revised 17 October 2011; accepted 25 October 2011.
ELDERLY INDIVIDUALS UNDERGOING selective serotonin reuptake inhibitor (SSRI) therapy are at a great risk for developing the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). We report a case where an elderly patient with depression, who experienced SSRI-induced SIADH, was successfully treated using mirtazapine as an alternative antidepressant.
A 65-year-old Japanese man with depression was admitted to our hospital because of suicidal behavior. He had no previous history of any endocrine diseases. The results of the biochemical hematological tests – including that for serum Na level (143 mEq/L) – were normal. On day 10, sertraline therapy was initiated, and the dosage was gradually increased to 100 mg/day. On day 36, the patient's serum Na level decreased to 131 mEq/L, although he did not show any clinical symptoms of SIADH. The urinary osmolality (615 mOsm/kg), urine Na level (171 mEq/L), and serum creatinine level (0.72 mg/dL) were within the normal range, whereas the serum osmolality greatly decreased to 265 mOsm/kg. Thyroid-stimulating hormone, fT4, cortisol, aldosterone, and plasma renin activity were within the normal range. The results of physical examination suggested extracellular euvolemia. Sertraline was discontinued, and mirtazapine (30 mg/day) was initiated; 3 days later, the serum Na level returned to a normal value (142 mEq/L). Fortunately, the switching from sertraline to mirtazapine did not worsen but gradually relieved his depressive symptoms.
Arginine vasopressin (AVP) plays a crucial role in water balance and Na homeostasis. In SIADH, inappropriate secretion of AVP alters the regulation of free-water excretion and can result in hyponatremia, leading to a fatal outcome. The present patient had all the features of SIADH: serum osmolality < 275 mOsm/kg; urinary osmolality > 100 mOsm/kg; euvolemia, urinary Na level > 20 mEq/L; and normal thyroid and adrenal function. SSRI can lead to SIADH, although the exact mechanism remains unclear. SIADH has been reported to occur in approximately 0.06% of patients receiving SSRI.1 However, the frequency in the elderly population is extremely high and ranges from 12% to 33%.2 Therefore, the serum Na level of elderly individuals receiving SSRI should be closely monitored. SSRI-induced SIADH is likely to develop within the first month of the treatment.2
Liu et al.3 reported that the incidence of SSRI-induced SIADH is fairly equal for different SSRI. There is little evidence to suggest that using a different SSRI is safe for patients experiencing SSRI-induced SIADH. In our case, hyponatremia improved on switching from sertraline to mirtazapine therapy. Jagsch et al.4 reported an elderly patient with citalopram-induced SIADH who was safely re-challenged with mirtazapine. Mirtazapine might be considered as an alternative treatment option of patients with depression who develop SSRI-induced SIADH. The patient gave the authors informed consent to publish this letter.