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College of Pharmacy

HelixTalk Episode #120 - When it Rains it Pours: A Succinct Clinical Review of Hyponatremia due to SIADH

Date posted: October 13, 2020, 6:00 am

In this episode, we discuss the pathophysiology, drug-related causes, diagnosis, and treatment of a common type of hyponatremia called the syndrome of inappropriate antidiuretic hormone (SIADH).

Key Concepts

  1. SIADH causes hyponatremia by causing the body to reabsorb too much water and making the urine too concentrated. The core pathophysiology is a problem with water handling that leads to a sodium problem.
  2. SSRIs are the most common drug-induced cause of SIADH.  Other commonly implicated drugs are carbamazepine, oxcarbazepine, high-dose cyclophosphamide, and a variety of other CNS-acting medications.
  3. In acute or severe hyponatremia, 3% NaCl (hypertonic saline) is used to quickly increase serum sodium by about 6 mEq/L to avoid neurologic complications of hyponatremia.
  4. Fluid restriction (about 1-1.5 L/day) is the first-line therapy of SIADH management.  It takes several days for serum sodium to return back to normal levels.

References

  • Cuzzo B, Padala SA, Lappin SL. Vasopressin (Antidiuretic Hormone, ADH) [Updated 2020 Apr 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526069/
  • Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013;126(10 Suppl 1):S1-S42. doi:10.1016/j.amjmed.2013.07.006