Can Namenda (Memantine) Cause Hyponatremia?
Namenda (memantine) is not recognized as a cause of hyponatremia in clinical practice. There is no evidence in the medical literature, FDA labeling, or clinical guidelines linking memantine to hyponatremia or sodium disturbances.
Evidence Review
Medications That Do Cause Hyponatremia
Multiple drug classes are well-established causes of hyponatremia, but memantine is notably absent from these lists:
- Diuretics (thiazides, loop diuretics, indapamide) are frequent causes of hyponatremia through sodium depletion and impaired water excretion 1, 2
- Anticonvulsants (carbamazepine, sodium valproate) can cause SIADH-like syndrome with dose-dependent hyponatremia 3, 1, 4
- Antidepressants (including trazodone and SSRIs) place patients at particularly high risk for developing hyponatremia 3, 1
- Chemotherapeutic agents (cyclophosphamide, vincristine) are associated with hyponatremia 3
- Desmopressin administered perioperatively increases hyponatremia risk 3
Memantine's Pharmacokinetic Profile
The available evidence on memantine focuses exclusively on its renal excretion characteristics, not electrolyte disturbances:
- Memantine exposure increases 1.62-fold in mild renal impairment, 1.97-fold in moderate impairment, and 2.33-fold in severe impairment 5
- Dose reduction to 5 mg twice daily is recommended in severe renal impairment (creatinine clearance 5-29 mL/min) 6
- No dosage adjustments are needed for mild or moderate renal impairment 6
Clinical Implications
If a patient on memantine develops hyponatremia, look for alternative causes:
- Evaluate for concurrent medications known to cause hyponatremia (diuretics, antidepressants, anticonvulsants) 1
- Assess volume status to determine if hyponatremia is hypovolemic, euvolemic, or hypervolemic 7
- Check urine sodium and osmolality to distinguish between SIADH, cerebral salt wasting, and other etiologies 7
- Consider underlying conditions such as heart failure, cirrhosis, or malignancy that predispose to hyponatremia 7
Meticulous medication history is essential when evaluating hyponatremia, as drug-induced causes are common and reversible 1. However, based on current evidence, memantine should not be considered a culprit medication for sodium disturbances.