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Symptoms
  • presented with signs and symptoms of hyponatremia (eg, nausea, malaise, headache, lethargy, seizures, coma, respiratory depression) 
  • decreased serum sodium levels (101-109 mEq/L)
ACE Inhibitors
  • Frequency is unreported
  • ACE inhibitors alone can precipitate hyponatremia without co-administration of thiazide diuretics
  • hyponatremia induced by ACE inhibitors appears to be dilutional and is accompanied by features of SIADH
  • discontinuing the ACE inhibitor leads to resolution of the hyponatremia
  • Patients may show hypokalaemia if thiazide or loop diuretics are used concomitantly with ACE inhibitors
  •  
Mechanism & Risk
  • It is postulated that ACE inhibitors at low doses cannot block the conversion of angiotensin I to angiotensin II in the brain. Increased circulating angiotensin I is converted to angiotensin II in the brain causing thirst stimulation and consequently SIADH.
  • risk for hyponatremia may be greater in patients on concomitant diuretic therapy or who have congestive heart failure.
Calcium Channel Blockers
  • In theory, calcium channel antagonists with natriuretic properties could cause hyponatremia.
  • A case of amlodipine-associated hyponatremia has been reported.
  • calcium channel antagonist– related hyponatremia, if it exists, is extremely rare.
Management
  • In mild to moderate cases with a normovolaemic fluid status clinically, ceasing the offending drug and gentle fluid restriction would improve serum sodium levels gradually within a week.
  • In an acutely unwell patient due to severe drug induced hyponatraemia, severe fluid restriction or infusion of hypertonic saline may be require
  • May consider changing therapy and monitoring patient for improvement
Alternatives
  • Diuretics are not recommended as have higher likelihood of causing hyponatremia
  • ARBs are also established to cause hyponatremia and no available data on comparison with ACEi
  • Beta Blockers- Beta blockade, especially of the Beta 1 receptor at the macula densa, inhibits renin release, & the release of aldosterone. This causes hyponatermia and hyperkalemia
References:
  1. http://www.gpnotebook.co.uk/simplepage.cfm?ID=x20120201092040500242
  2. https://www.pjms.com.pk/issues/aprjun207/article/casereport3.html
  3. Jenny A. Van Amburgh. Can Lisinopril Cause Hyponatremia? - Medscape - Jul 28, 2011
  4. American Journal of Kidney Diseases, Vol 52, No 1 (July), 2008: pp 144-153

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