Fact check: What are the most common side effects of memantine in patients over 65?

1. What the older literature says — side effects catalogued and their tone of risk

A 2009 review described memantine’s adverse effects as mild and transient, listing constipation, dizziness, headache, and confusion among the most commonly observed events; the review framed these effects as relevant to older patients and indicative of a generally acceptable tolerability profile ^[1]. That earlier synthesis reflects clinical trial data and post‑marketing reports available up to that date, and its emphasis on mildness signals an overall benefit‑risk judgment favoring memantine for symptomatic management. The review does not, however, provide granular incidence rates by age band, which leaves open how frequency or severity might shift in people over 65.

2. Recent programmatic assessments — the 2024 perspective on tolerability

A 2024 report reiterated that memantine is typically well tolerated, specifically identifying dizziness and headache as commonly reported adverse events in treated patients, thereby aligning closely with the 2009 characterization ^[2]. The 2024 framing benefits from additional clinical experience and pharmacovigilance accumulated over the intervening years, but it remains a broad safety statement rather than an age‑stratified risk analysis. The report’s emphasis on continued tolerability suggests no major emergent safety signals by mid‑2024, yet it does not resolve whether older adults experience different frequencies or severities of these side effects compared with younger cohorts ^[2].

3. Newer mortality findings shift the conversation but not side‑effect granularity

A 2025 systematic review and meta‑analysis reported an association between long‑term memantine treatment and a reduction in all‑cause mortality among patients with major cognitive disorders, a clinically significant outcome that reframes memantine’s net benefit calculation ^[3]. Importantly, this meta‑analysis did not provide specific data on side‑effect patterns for patients aged over 65, so while the mortality signal strengthens arguments for memantine’s overall clinical utility, it does not replace the need for age‑specific adverse‑event data. The absence of stratified safety data is a substantive evidence gap when making geriatric prescribing decisions.

4. Reconciling consistent side‑effect listings with missing age‑specific incidence

Across the three sources, a consistent set of common adverse events—dizziness, headache, constipation, and confusion—emerges, suggesting robust agreement on the symptom profile even as methodological scope varies ^{[1] [2]}. However, none of the provided analyses supply precise incidence percentages or comparative rates for those over 65, which prevents definitive statements about how often these effects occur in that age group. The consensus on event types therefore supports clinical vigilance for these symptoms in older patients, but exact risk quantification for decision‑making and counseling is not available in the supplied evidence.

5. Interpreting the evidence given likely biases and context gaps

Each source has potential limitations and agendas: the 2009 review summarizes earlier trials and may under‑report rarer harms; the 2024 report reflects contemporary viewpoints that favor reassurance about tolerability; and the 2025 meta‑analysis prioritizes mortality outcomes without detailed adverse‑event stratification ^{[1] [2] [3]}. Treating these sources as complementary rather than identical is necessary: they jointly endorse memantine’s tolerability and possible mortality benefit, yet they collectively fail to deliver the specific incidence data clinicians need for geriatric counseling. This pattern signals both converging evidence and an unmet need for targeted geriatric safety studies.

6. Practical takeaways for clinicians and patients over 65

Given the evidence supplied, clinicians should anticipate and monitor for dizziness, headache, constipation, and transient confusion when prescribing memantine to patients over 65, counsel patients and caregivers accordingly, and weigh the drug’s potential mortality benefit reported in 2025 against individual comorbidities and concomitant medications ^{[1] [2] [3]}. Because age‑specific incidence data are lacking in these analyses, clinicians should use routine geriatric safety practices—dose titration, fall‑risk assessment, bowel regimen planning, and active adverse‑effect surveillance—to manage likely side effects while considering memantine’s overall benefit profile.

7. Where the evidence needs to go next — targeted research priorities

To resolve remaining uncertainties, future studies must report age‑stratified side‑effect rates and interactions with common geriatric comorbidities and polypharmacy; the current corpus offers consistent symptom lists but not the frequency or severity specific to patients over 65 ^{[1] [2] [3]}. Randomized trials or large observational cohorts that prespecify older age bands, measure functional outcomes linked to adverse events (e.g., falls, hospitalizations), and balance mortality signals against harms would directly address the evidence gap highlighted across the provided sources.