August, 27 2025

One medicine won’t stop Alzheimer’s or Parkinson’s dementia-but it can help people think a little clearer, function a bit better, and feel calmer. That medicine is memantine. If you’re weighing whether it’s worth starting, here’s the straight answer: it offers modest symptom relief in the right conditions, comes with a manageable side-effect profile, and needs a fair trial before you judge it.

• TL;DR: Best evidence is for moderate-to-severe Alzheimer’s disease. Expect small but meaningful gains in cognition, daily function, and behavior within 8-12 weeks.
• Who else might benefit: some people with dementia with Lewy bodies or Parkinson’s disease dementia (especially for global function/behavior). Not helpful in frontotemporal dementia.
• How it works: uncompetitive NMDA receptor antagonist; reduces glutamate-driven excitotoxicity without dulling normal brain signaling.
• How to use: start low and go slow-5 mg daily, increase by 5 mg each week to 20 mg/day if tolerated. Adjust for kidney disease.
• When to stop: if there’s no clear benefit after 3 months at the target dose, or if side effects outweigh gains; reassess and deprescribe thoughtfully.

Where this medicine helps-and where it doesn’t

Think of memantine as a symptom manager, not a disease-stopping therapy. It won’t halt neurodegeneration, but it can reduce the noise-too much glutamate-from damaged circuits, which may translate to better attention, fewer confusional episodes, steadier mood, or less agitation.

Alzheimer’s disease (AD): This is where memantine earns its spot. Multiple randomized trials and meta-analyses show small-to-moderate improvements in cognition, global status, and daily activities in moderate-to-severe AD. On rating scales, the average effect is modest, but for families, even a few points can mean handling meals, dressing, or conversations more smoothly.

What to expect in practice: improvements usually show up by 8-12 weeks and can be easiest to notice in day-to-day routines-fewer repetitive questions, less sundowning, or fewer agitated outbursts. Some people sleep better. Not everyone responds. A fair trial means reaching the target dose and giving it time.

Combination with cholinesterase inhibitors: Pairing memantine with donepezil, rivastigmine, or galantamine can bring extra benefit in moderate-to-severe AD. Trials like DOMINO-AD and pooled analyses suggest continuing a cholinesterase inhibitor remains the bigger driver of benefit; memantine adds a modest layer, especially on behavior and global function. If someone can’t tolerate a cholinesterase inhibitor (nausea, bradycardia), memantine alone is a reasonable option.

Dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD): The signal is mixed but encouraging for overall clinical impression and behavior. Cholinesterase inhibitors remain first-line. Memantine may help agitation or attention in some people, though a minority experience worsened confusion or hallucinations. Start low and watch closely.

Vascular cognitive impairment/dementia: Evidence shows small cognitive gains, but licensing is inconsistent and guidelines differ by country. In the UK, routine use for pure vascular dementia isn’t recommended; consider it only if mixed AD features are likely.

Frontotemporal dementia (FTD): Not helpful. Trials failed to show benefit, and behavior can worsen. If there’s diagnostic uncertainty between FTD and AD, be cautious and reassess quickly.

Huntington’s disease, ALS, multiple sclerosis, traumatic brain injury: No convincing benefit in cognition or disease course. It’s not a fix for general “brain fog.”

Behavioral symptoms and caregiver burden: Even when memory scores barely budge, fewer agitated episodes or nighttime confusion can reduce stress for families. Some observational studies link memantine use to delayed institutionalization, but those studies can’t prove cause and effect. Treat such claims as promising, not guaranteed.

Bottom line fit: If the diagnosis is moderate-to-severe Alzheimer’s, memantine is worth a structured trial. In DLB or PDD, it’s a thoughtful add-on after a cholinesterase inhibitor if behavior or global function are top concerns. Avoid in FTD. Keep expectations realistic: we’re talking nudges, not turnarounds.

Getting treatment right: dosing, safety, and monitoring

Dosing (immediate-release tablets):

• Week 1: 5 mg once daily
• Week 2: 10 mg/day (5 mg twice daily)
• Week 3: 15 mg/day (10 mg morning, 5 mg evening)
• Week 4 and onward: 20 mg/day (10 mg twice daily), if tolerated

Extended-release capsules (where available): once-daily titration to the licensed target (varies by region). In the UK, immediate-release is common and simple.

Kidney function adjustments:

• Mild impairment (eGFR ≥50 mL/min): usual target 20 mg/day
• Moderate (eGFR 30-49): start 5 mg/day; typical target 10 mg/day; some people can cautiously increase to 20 mg/day if well tolerated
• Severe (eGFR 5-29): target 10 mg/day

Liver disease: use caution. In moderate to severe hepatic impairment, discuss risks and go slow.

When to take it: mornings suit many. If sleep becomes fractured or vivid dreams pop up, try moving the evening dose earlier. Consistency helps caregivers spot patterns.

Common side effects:

• Dizziness or headache (often settle within 1-2 weeks)
• Constipation (add fluids, fibre, gentle movement; consider a stool softener if needed)
• Sleep changes or vivid dreams
• Raised blood pressure in a small subset-check periodically
• Confusion or hallucinations in a minority, more likely in DLB/PDD

Drug interactions to know:

• Other NMDA antagonists (amantadine, ketamine, dextromethorphan): higher risk of side effects; avoid combinations unless a specialist says otherwise.
• Urine alkalinizers (for example, sodium bicarbonate) or conditions that raise urine pH can reduce memantine clearance and raise blood levels. If a new antacid regimen starts, watch for dizziness or confusion.
• Anticholinergics (like some bladder or allergy meds): can worsen confusion; review the whole list of medicines.

Food and drink: no special food restrictions. Stay hydrated. Alcohol can amplify dizziness; keep it modest or avoid if balance is an issue.

How to monitor benefit (what to track every 4-12 weeks):

• Thinking: attention span, following steps, sticking with a TV plot or conversation
• Function: dressing, bathing, meal prep, handling the phone or remote
• Behavior: agitation, irritability, sleep-wake cycle, nighttime wandering, hallucinations
• Caregiver load: time spent cueing, number of distressing episodes per day/week

Simple goal-setting helps: pick 2-3 things that matter most (“fewer evening outbursts,” “finish breakfast without getting stuck,” “sleep from midnight to 6am”). If those goals improve at the target dose, you’re seeing meaningful benefit even if test scores barely change.

What if agitation flares after starting?

• Hold the dose where it is for 1-2 weeks to see if it settles. Many side effects fade.
• If hallucinations or severe distress appear, step back to the last well-tolerated dose or pause and call the prescriber.
• Check triggers: infections, new medicines (anticholinergics, sedating antihistamines), pain, dehydration, constipation.

Stopping and deprescribing:

• If there’s no clear benefit after 3 months at a stable target dose, consider tapering off.
• How to stop: reduce by 5 mg each week (for example, 20 → 15 → 10 → 5 → stop). If cognition or behavior clearly worsens, you can restart.
• Consider stopping in late-stage disease when eating is poor, weight is falling, or side effects (like repeated dizziness and falls) dominate.

Practical safety checks at home:

• Use a weekly pill box and a simple one-page med list on the fridge for anyone helping with care.
• Record two things daily for the first month: “good hours” (calmer, engaged) and any side effects. Patterns jump out.
• Keep a hydration routine-confusion worsens fast when people are dry.

Evidence, choices, and practical tools

What the research says (short version):

• Mechanism: memantine is a low-to-moderate affinity NMDA receptor blocker with fast off-rate and voltage-dependent binding. In plain English, it dampens harmful overactivation without shutting down normal learning signals.
• Alzheimer’s disease: Multiple randomized trials and pooled analyses show small-to-moderate improvements versus placebo in moderate-to-severe stages, with measurable effects on cognition, global ratings, and daily function. Benefits tend to be largest in behavior and clinician global impression scores.
• Combination therapy: Adding memantine to a cholinesterase inhibitor offers incremental benefit for many, though continuing the cholinesterase inhibitor drives the bigger effect.
• DLB/PDD: Mixed results. Some trials show improvements in global function or behavior. Hallucinations can worsen in a minority-watch and adjust.
• FTD: No benefit; sometimes worse behavior. Not recommended.

Guideline signals you can trust: NICE guidance in the UK supports memantine for moderate-to-severe Alzheimer’s and considers it when cholinesterase inhibitors aren’t tolerated. International statements from neurology and geriatric societies echo this stance. Cochrane reviews and recent meta-analyses back the modest effect sizes and the safety profile seen in practice.

Decision help: when to consider memantine first, add it, or avoid it

• Start first-line: moderate-to-severe Alzheimer’s where agitation, attention, or day-to-day function are key goals and a cholinesterase inhibitor isn’t suitable.
• Add-on: already on donepezil/rivastigmine/galantamine with ongoing behavior or function issues; caregiver goals focus on calm evenings, fewer outbursts, or clearer mornings.
• Not for: frontotemporal dementia; mild cognitive impairment; mild AD with no functional change; non-degenerative “brain fog.”

Quick comparison vs. cholinesterase inhibitors (ChEIs):

• Main targets: ChEIs boost acetylcholine; better for memory/attention in earlier AD and for hallucinations in DLB/PDD. Memantine calms glutamate noise; can be more helpful for behavior in later AD.
• Side effects: ChEIs often cause nausea, diarrhea, weight loss, bradycardia. Memantine is more likely to cause dizziness, constipation, blood pressure bumps.
• Use together? Often yes in moderate-to-severe AD, if tolerated.

Rules of thumb you can use today:

• Give it time: don’t judge before 8-12 weeks at the right dose.
• Measure what matters: pick 2-3 family goals; don’t rely only on test scores.
• Start low, go slow, and adjust for kidneys.
• Watch the bladder meds: anticholinergics undermine thinking and can blunt any gain you get from dementia meds.
• If new hallucinations appear, reassess dose, look for infections, and review other meds first.

Caregiver checklist (print-and-stick):

• We started on: [date]. Target goals: [list 2-3].
• Week-by-week plan: increase by 5 mg each week to [10/15/20] mg/day as agreed.
• Side effects to watch: dizziness, constipation, sleep changes, confusion.
• Call the prescriber if: severe hallucinations, falls, fainting, blood pressure spikes, or no benefit after 12 weeks.
• Track “good hours” daily for the first month.

Mini-FAQ

Q: Will memantine slow the disease? A: No. It eases symptoms. Disease-modifying drugs for Alzheimer’s exist in some countries, but access and suitability vary. Memantine can still help with day-to-day function.

Q: How big are the gains, really? A: On average, small. But if evenings go from chaotic to manageable, that’s a big win for families-even if the average study effect size looks modest.

Q: Can I combine it with donepezil? A: Yes, commonly done in moderate-to-severe AD. If side effects crop up, adjust one thing at a time so you know what caused what.

Q: What if my partner has Lewy body dementia? A: Prioritize a cholinesterase inhibitor. If behavior stays rough, a cautious memantine trial is reasonable, with close watch for hallucinations.

Q: Is it expensive? A: It’s generic and low-cost in the UK. On the NHS, the barrier is usually clinical fit, not price.

Q: We saw no change-was it a waste? A: Not a waste, but a result. If you gave a fair trial and saw no gain, taper and stop. You can focus on non-drug strategies and review other meds that cloud thinking.

Next steps and troubleshooting

• If you’re a caregiver starting therapy: write down two goals, set reminders for weekly dose changes, and schedule a 12-week review.
• If you’re a GP or clinician: check baseline blood pressure, eGFR, and the med list for anticholinergics or interacting agents; set shared goals before you prescribe.
• If behavior worsens after an increase: pause titration, step back to the last good dose, and screen for infection, pain, dehydration, or new meds.
• If dizziness leads to near-falls: split the dose morning and early evening, review blood pressure meds, consider a slower titration or lower target.
• If constipation becomes a problem: add fibre, fluids, gentle activity; consider a stool softener or osmotic laxative.
• If there’s no benefit at 12 weeks: taper in 5 mg steps weekly. If decline follows, consider restarting at the last helpful dose.

Evidence and credibility notes: The guidance in this article reflects UK practice in 2025 and aligns with NICE dementia guidance, the European product information for memantine, Cochrane reviews, and meta-analyses across the last decade. The clinical experience piece-start low, go slow, measure what matters-matches what geriatricians and memory clinics use day to day. Always tailor decisions to diagnosis, comorbidities, and the goals that matter to the person and their family.