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Last edited on April 30, 2020

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--- cl:hyponatremia [on April 30, 2020]
+++ cl:hyponatremia [on December 27, 2021] (current)
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 Hyponatremia is frequently underdiagnosed and undertreated in both general medicine and psychiatric patients.[([[https://www.ncbi.nlm.nih.gov/pubmed/18306096|Siegel, A. J. (2008). Hyponatremia in psychiatric patients: update on evaluation and management. Harvard review of psychiatry, 16(1), 13-24.]])] Like with other electrolyte and fluid imbalances (see also: [[cl:hypokalemia|hypokalemia]], [[cl:hypomagnesemia|hypomagnesemia]], [[cl:hypocalcemia|hypocalcemia]], [[cl:hypercalcemia-hyperparathyroidism|hypercalcemia]]),[([[https://www.ncbi.nlm.nih.gov/pubmed/7220784|Webb Jr, W. L., & Gehi, M. (1981). Electrolyte and fluid imbalance: neuropsychiatric manifestations. Psychosomatics, 22(3), 199-203.]])] hyponatremia can cause neuropsychiatric symptoms. Acute-onset hyponatremia can cause delirium and acute behavioural changes that can be mistaken for symptoms of a psychiatric disorder. Other causes of hyponatremia, such as SIADH, may resemble psychiatric disorders or the adverse effects of psychotropic drugs, and the diagnosis of SIADH can be delayed for psychiatric patients.
 </callout>
+===== Approach =====
+<panel type="info" title="Hyponatremia Etiologies" subtitle="" no-body="true" footer="* = Most medications that cause hyponatremia do so by triggering inappropriate ADH secretion">
+^ Too much water going in     | Water intoxication                                                                         |
+^ Too little water going out  | Excessive antidiuretic hormone (ADH)*                                                      |
+^ Too little sodium going in  | Poor IV fluid management post-operatively or general dehydration                           |
+^ Too much sodium going out   | • Aldosterone or cortisol deficiency \\ • Diuretic use \\ • Diarrhea, burns, or vomitting  |
+</panel>
 ===== Symptoms =====
 Early signs and symptoms of hyponatremia includes nausea, vomiting, anorexia, disorientation, headache, fatigue, weakness, irritability, lethargy, confusion, and muscle cramps.[([[https://www.ncbi.nlm.nih.gov/pubmed/7220784|Webb Jr, W. L., & Gehi, M. (1981). Electrolyte and fluid imbalance: neuropsychiatric manifestations. Psychosomatics, 22(3), 199-203.]])] Falls and confusion in the due to hyponatremia is common in the elderly.[([[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4110800/|Soiza, R. L., & Talbot, H. S. (2011). Management of hyponatraemia in older people: old threats and new opportunities. Therapeutic advances in drug safety, 2(1), 9-17.]])] With severe hyponatremia, [[neurology:approach-seizures|seizures]] can develop.
-<imgcaption fig1|>{{ :cl:hyponatremia-approach.png?800|Approach to Hyponatremia, (from Papadakis M.A., McPhee S.J., Rabow M.W. Eds. Maxine A. Current Medical Diagnosis & Treatment 2017 New York, NY: McGraw-Hill)}}</imgcaption>
+<imgcaption fig1|>{{:cl:hyponatremia-approach.png?800|Approach to Hyponatremia, (from Papadakis M.A., McPhee S.J., Rabow M.W. Eds. Maxine A. Current Medical Diagnosis & Treatment 2017 New York, NY: McGraw-Hill)}}</imgcaption>
 ===== Etiologies =====
 There are numerous etiologies of hyponatremia. The correct treatment and management of hyponatremia depends on identifying the etiology of the hyponatremia. For example, one must differentiate between iatrogenic hyponatremia (typically due to thiazide diuretics, carbamazepine, antidepressants, or antipsychotics), idiopathic hyponatremia, or other etiologies (like hypothyroidism or alcoholism). Generally speaking, the majority of hyponatremias in the psychiatric population are associated with physiologically inappropriate (but not necessarily elevated) levels of arginine vasopressin (AVP), leading to water retention and serum hypotonicity.
+==== SIADH ====
+<alert type="info" icon="fa fa-book fa-lg fa-fw">
+See also: **[[https://pubmed.ncbi.nlm.nih.gov/16896026/|Jacob, S., & Spinier, S. A. (2006). Hyponatremia associated with selective serotonin-reuptake inhibitors in older adults. Annals of Pharmacotherapy, 40(9), 1618-1622.]]**
+</alert>
+**Syndrome of inappropriate antidiuretic hormone secretion (SIADH)** can cause hyponatraemia.[([[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1335030|Liu, B. A., Mittmann, N., Knowles, S. R., & Shear, N. H. (1996). Hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone associated with the use of selective serotonin reuptake inhibitors: a review of spontaneous reports. CMAJ: Canadian Medical Association Journal, 155(5), 519.]])] Many psychotropic medications can cause SIADH either by stimulating the release of vasopressin or by potentiating its action on the renal tubules. It is also thought that psychotropics may cause stimulation of central serotonin receptors as well. SIADH is a known side effect of antidepressants, especially in the elderly.
+SIADH is characterized by the following sequence of:
+  - Excessive free water retention
+  - Euvolemic hyponatremia with continued urinary sodium excretion
+  - Urine osmolality > serum osmolality
+Severe hyponatremia from SIADH can result in cerebral edema, and/or seizures. The treatment of SIAD consists of: (1) fluid restriction (first line), (2) salt tablets, (3) diuretics, (4) ADH antagonists, and/or (5) a slow correction of the hyponatremia with hypertonic saline to avoid osmotic demyelination syndrome (central pontine myelinolysis).
 ==== Psychogenic Polydipsia ====
 **Psychogenic polydipsia (PPD)** (also known as primary polydipsia) is excessive and volitional water intake commonly patients with severe mental illness and/or developmental disability. Psychogenic polydipsia can cause hyponatremia, and is associated with minor impairments in water excretion.[([[https://www.ncbi.nlm.nih.gov/pubmed/2189300|Cheng, J. C., Zikos, D., Skopicki, H. A., Peterson, D. R., & Fisher, K. A. (1990). Long-term neurologic outcome in psychogenic water drinkers with severe symptomatic hyponatremia: the effect of rapid correction. The American journal of medicine, 88(6), 561-566.]])] Psychogenic Polydipsia and PIP Syndrome can be considered synonymous diagnoses.
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 ==== Antidepressants ====
-The incidence of hyponatremia caused by SSRIs varies widely, from 0.5% to 32%. In the majority of cases, hyponatremia occurs within the first few weeks of the onset of therapy. The hyponatremia typically resolves 2 weeks after discontinuation of the SSRI.[([[https://www.ncbi.nlm.nih.gov/pubmed/16896026|Jacob, S., & Spinier, S. A. (2006). Hyponatremia associated with selective serotonin-reuptake inhibitors in older adults. Annals of Pharmacotherapy, 40(9), 1618-1622.]])]
+The incidence of hyponatremia caused by SSRIs varies widely, from 0.5% to 32%. In the majority of cases, hyponatremia occurs within the first 2 to 4 weeks of the onset of therapy. The hyponatremia typically resolves 2 weeks after discontinuation of the SSRI, and the incidence returns back to population baseline after 3 months.[([[https://pubmed.ncbi.nlm.nih.gov/27194321/|Leth-Møller, K. B., Hansen, A. H., Torstensson, M., Andersen, S. E., Ødum, L., Gislasson, G., ... & Holm, E. A. (2016). Antidepressants and the risk of hyponatremia: a Danish register-based population study. BMJ open, 6(5).]])][([[https://www.ncbi.nlm.nih.gov/pubmed/16896026|Jacob, S., & Spinier, S. A. (2006). Hyponatremia associated with selective serotonin-reuptake inhibitors in older adults. Annals of Pharmacotherapy, 40(9), 1618-1622.]])]
+<panel type="info" title="Hyponatremia Risk" subtitle="" no-body="true" footer="">
+^ Higher Risk                                                              ^ Lower Risk           ^
+| SSRIs (class effect), >5%                                                | Mirtazapine (2.5%)   |
+| SNRIs (venlafaxine, duloxetine)                                          | MAOis (moclobemide)  |
+| TCAs (noradrenergic ones such nortripyline, lofepramine might be safer)  |                      |
+</panel>
 ==== Antipsychotics ====
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 It is important to differentiate between psychotropic-induced SIADH and psychogenic polydipsia. SIADH should be a diagnosis of exclusion. To differentiate between SIADH and psychogenic polydipsia, it is important to measure serum sodium, osmolality, and urine osmolality.
+===== Comparison =====
+{{page>cl:hypercalcemia-hyperparathyroidism#comparison&nouser&noheader&nodate&nofooter}}
 ===== Treatment and Management =====
   * [[https://www.uspharmacist.com/article/management-of-hyponatremia|Guirguis, E., & Seetaram, M. (2013). Management of Hyponatremia: Focus on Psychiatric Patients. US Pharm, 11, 15.]]