From the FDA Drug Label
Memantine is excreted predominantly (about 48%) unchanged in urine and has a terminal elimination half-life of about 60 to 80 hours Renal clearance involves active tubular secretion moderated by pH dependent tubular reabsorption. Memantine pharmacokinetics were evaluated following single oral administration of 20 mg memantine HCl in 8 subjects with mild renal impairment (creatinine clearance, CLcr, >50 to 80 mL/min), 8 subjects with moderate renal impairment (CLcr 30 to 49 mL/min), 7 subjects with severe renal impairment (CLcr 5 to 29 mL/min) and 8 healthy subjects (CLcr > 80 mL/min) matched as closely as possible by age, weight and gender to the subjects with renal impairment. Mean AUC0-∞ increased by 4%, 60%, and 115% in subjects with mild, moderate, and severe renal impairment, respectively, compared to healthy subjects. No dosage adjustment is recommended for patients with mild and moderate renal impairment. Dosage should be reduced in patients with severe renal impairment [see Dosage and Administration (2)]
Key Points:
- Memantine is eliminated in part by the kidneys.
- Renal impairment can affect memantine pharmacokinetics.
- Dosage adjustment is recommended for patients with severe renal impairment.
Memantine does affect renal function, as it is eliminated in part by the kidneys and renal impairment can affect its pharmacokinetics 1.
From the Research
Namenda (memantine) can be affected by renal function and requires dose adjustments in patients with kidney impairment. The most recent and highest quality study on this topic is from 2012 2, which suggests that the dose of memantine should be halved in patients with renal impairment.
Key Points to Consider
- For patients with moderate renal impairment (creatinine clearance 30-49 mL/min), the recommended target dose is reduced to 10 mg twice daily instead of the standard 20 mg daily.
- In severe renal impairment (creatinine clearance 5-29 mL/min), the target dose should be further reduced to 5 mg twice daily, as suggested by a study in 2006 3.
- Memantine is primarily eliminated unchanged through the kidneys, and reduced kidney function leads to decreased drug clearance and potentially higher blood levels of the medication.
- Without appropriate dose adjustments, patients with renal impairment may experience increased side effects such as dizziness, headache, confusion, or constipation.
- Regular monitoring of kidney function is recommended for patients taking Namenda, especially in elderly patients who may have age-related decline in renal function.
- The medication itself is not known to cause kidney damage, but proper dosing based on renal function is essential for safe use, as highlighted in a review of memantine's use in Alzheimer's disease in 2006 4.
- A case report in 2013 5 also suggests that memantine may be associated with hyperkalaemia in patients with renal impairment, further emphasizing the need for careful dose adjustment and monitoring.
- Additionally, a study in 2020 6 found that pre-existing chronic kidney disease increases the risk of mortality in critically ill patients, highlighting the importance of considering renal function when prescribing medications like Namenda.