Can Losartan Cause Hyponatremia?
Yes, losartan can cause hyponatremia, though it is a rare adverse effect compared to other medications. This has been documented in case reports, with severe cases requiring medical intervention 1.
Evidence for Losartan-Induced Hyponatremia
Case Reports and Clinical Evidence
- A case report documented severe hyponatremia (serum sodium 123 mEq/L) in a 73-year-old diabetic patient after 3.5 months of losartan 50 mg daily therapy 1
- Another study reported 40 cases of hyponatremia associated with losartan/hydrochlorothiazide combination (Preminent®), with an average lowest sodium value of 114.4 mEq/L 2
- In this study, symptoms developed either progressively (within 50 days) or after precipitating factors like fever or appetite loss (after 50 days)
- Recovery typically occurred within 6.8 days after discontinuation
Mechanism and Risk Factors
Losartan, as an angiotensin II receptor blocker (ARB), may cause hyponatremia through:
- Interference with the renin-angiotensin-aldosterone system
- Potential enhancement of antidiuretic hormone (ADH) effects
- Altered renal sodium handling
Risk factors that may increase susceptibility include:
- Advanced age (most reported cases were in elderly patients)
- Concomitant use of other medications that can cause hyponatremia
- Underlying renal dysfunction
- Volume depletion states
Clinical Management Considerations
Monitoring
For patients on losartan therapy:
- Monitor serum electrolytes, particularly in high-risk patients (elderly, those with renal impairment)
- Be vigilant for symptoms of hyponatremia: confusion, drowsiness, weakness, headache
- Consider more frequent monitoring during the first few months of therapy
Treatment of Losartan-Induced Hyponatremia
If hyponatremia develops:
- Assess severity of symptoms and sodium level
- Consider discontinuation of losartan (de-challenge)
- Provide appropriate sodium correction based on acuity and severity
- Avoid overly rapid correction to prevent central pontine myelinolysis
Alternative Medications
If hyponatremia occurs with losartan, consider alternative antihypertensive medications:
- Calcium channel blockers (amlodipine, felodipine) may be suitable alternatives in patients with hypertension 3
- ACE inhibitors may not be appropriate alternatives as they share similar mechanisms and potential for hyponatremia
Special Populations and Considerations
Elderly Patients
Elderly patients appear to be at higher risk for losartan-induced hyponatremia:
- The mean age in the case series of 40 patients was 76.4 years 2
- Careful monitoring of electrolytes is particularly important in this population
Patients with Heart Failure
For patients with heart failure:
- Hyponatremia is a potential concern with ARB therapy
- The European Society of Cardiology notes that ARBs should be used with caution in certain populations 3
- Monitoring for electrolyte disturbances is recommended when using ARBs in heart failure patients
Conclusion
While hyponatremia is not among the most common adverse effects of losartan, case reports indicate it can occur, particularly in elderly patients. Clinicians should be aware of this potential adverse effect and monitor patients accordingly, especially those with risk factors for developing electrolyte disturbances.