Memantine (Namenda)

What it treats

Memantine is approved by the U.S. Food and Drug Administration for moderate to severe Alzheimer's disease dementia. In mild disease the evidence is thin and it isn't recommended as a first choice.

It's often combined with a cholinesterase inhibitor once someone has moved from mild to moderate disease. A combination product (Namzaric) pairs memantine ER with donepezil in a single capsule for convenience. Off-label, memantine is sometimes tried in vascular dementia, Lewy body dementia, and other conditions, with mixed evidence.

How it works

In Alzheimer's disease, glutamate signaling through NMDA receptors seems to become chronically overactive at a low level, contributing to background excitotoxic stress on neurons and muddying normal signaling. This isn't the sharp glutamate signal that carries useful information; it's more like background noise that never quite turns off.

Memantine sits in the NMDA receptor channel at a low affinity, blocking that pathological low-level signal, but it releases from the channel when a strong normal signal comes through. That "uncompetitive" behavior is the point: it filters out the background noise without blocking normal neurotransmission. The result is modest symptomatic benefit in moderate to severe disease.

Receptor mechanism (detail)

Memantine is an uncompetitive, moderate-affinity antagonist of the NMDA glutamate receptor. It sits in the open channel and blocks pathological, tonic glutamate signaling but releases with normal phasic signaling, which is why it doesn't cause the cognitive impairment of higher-affinity NMDA antagonists like ketamine. It has some activity at other receptors (serotonin 5-HT3, nicotinic acetylcholine, sigma-1) but the NMDA mechanism is the one that matters clinically.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

Immediate release: start 5 mg once daily. After 1 week, increase to 5 mg twice daily. After another week, increase to 10 mg in the morning and 5 mg in the evening. After another week, target 10 mg twice daily.

Extended release (Namenda XR): start 7 mg once daily and increase weekly by 7 mg to a target of 28 mg once daily.

Renal dose adjustment: reduce the maintenance dose to 5 mg BID (IR) or 14 mg daily (ER) in people with a creatinine clearance under 30 mL/min. Memantine is cleared by the kidneys, and this matters a lot in older adults.

Safety monitoring

• Kidney function (creatinine, eGFR) at baseline and periodically. Reduced clearance means higher blood levels at the same dose, more side effects.
• Blood pressure. Some people see a modest rise.
• Confusion or worsening cognition. Uncommon but can happen, especially at higher doses or in renal impairment.
• Falls and dizziness, especially in the first weeks.
• Sedation. Usually mild but worth asking about.

Memantine doesn't require the heart-rate and GI monitoring that the cholinesterase inhibitors do. That's a real practical advantage in the older-adult population.

What to expect

As with the cholinesterase inhibitors, the effect is a slower slope of decline rather than an obvious improvement. Over 3 to 6 months, families sometimes notice better engagement, less agitation, or slower loss of function than they'd been expecting. Formal cognitive scores drift down more slowly than they would without treatment. It's not a rescue drug.

The tolerability story is different from the cholinesterase inhibitors and mostly in a good way. GI side effects are uncommon. The main early complaints are mild dizziness, headache, or a bit of confusion at dose steps, and they usually settle. Slow titration prevents most of the trouble.

Memantine is often added to a cholinesterase inhibitor rather than replacing it, on the theory that hitting two different chemical systems helps a bit more than either alone. The added benefit is modest but real.

Common side effects

Most people tolerate memantine well. When side effects come, they're usually mild.

• Dizziness.
• Headache.
• Confusion, especially early or at dose steps.
• Constipation.
• Fatigue.
• Modest blood pressure increase.
• Sleepiness.

Slow titration is the main way to reduce these. If dizziness or confusion is a problem, holding the current dose for an extra week or two before stepping up often solves it.

Serious side effects and warnings

Serious problems are uncommon.

• Confusion or delirium. Rare, but can happen, especially in renal impairment or at doses higher than recommended.
• Cardiovascular effects. Modest blood pressure and heart rate changes have been reported.
• Seizures. Rare.
• Serious skin reactions. Very rare but reported.

The absence of the classic cholinesterase-inhibitor problems (bradycardia, severe GI toxicity, GI bleeding) is one of memantine's practical selling points.

Sexual and relational effects

Memantine isn't a notable cause of sexual side effects. The relational conversation is similar to the other dementia drugs: care partners are hoping for the person to become more like themselves again. The honest expectation is a slower decline and, sometimes, a modest bump in engagement or a reduction in agitation. That can matter a lot for a family managing daily care, even when the change is small.

Weight, appetite, and sleep

Memantine has much less impact on weight, appetite, and sleep than the cholinesterase inhibitors. Constipation is a more common GI complaint than nausea. Weight loss isn't a typical concern. Sleep effects are usually neutral, with occasional mild sedation or, less often, mild sleep disruption.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The right dose is a decision for a prescriber.

Memantine comes as IR tablets (5, 10 mg), an oral solution, and ER capsules (7, 14, 21, 28 mg). The ER form is once daily and generally preferred for adherence. Combination products with donepezil (Namzaric) are available in a few strengths.

Titration is weekly. Slower titration is fine if side effects are marginal. Dose reduction is required for CrCl under 30 mL/min.

Missed doses and interactions

If a dose is missed, take it when remembered unless it's close to the next scheduled dose. Don't double up. If several days have been missed, it's reasonable to restart at the current dose (memantine doesn't have the severe-vomiting-on-restart problem that the cholinesterase inhibitors do), but check with the prescriber.

Interactions to know:

• Drugs that alkalinize the urine (sodium bicarbonate, carbonic anhydrase inhibitors like acetazolamide) reduce memantine clearance and raise levels.
• Other NMDA antagonists (amantadine, dextromethorphan, ketamine) can have additive effects.
• Hydrochlorothiazide combinations may lower hydrochlorothiazide levels.

The interaction profile is much cleaner than the cholinesterase inhibitors. Give every prescriber a full medication list anyway.

Stopping and tapering

Memantine doesn't cause a classic withdrawal, but stopping can be followed by a step-down in cognition or function that may not fully recover on restart. If the plan is to stop, tapering down over a couple of weeks and watching for a change is safer than a hard stop.

Reasons to stop include lack of clear benefit, intolerable side effects (uncommon), and end-of-life care. In advanced disease, the balance shifts and stopping often becomes reasonable.

Pregnancy and breastfeeding

This isn't a routine issue given the patient population. Memantine isn't used in pregnancy or breastfeeding in ordinary practice. Anyone in an unusual clinical situation involving reproductive planning should discuss it with a specialist.

Cost and generic availability

Generic memantine, both IR and ER, is available and inexpensive. The combination with donepezil (generic memantine/donepezil) is also available. Brand-name Namenda and Namzaric are still on the market but generally unnecessary.

Common questions

Is memantine the same as the "Alzheimer's medication"? There are really two classes of older Alzheimer's drugs. The cholinesterase inhibitors (donepezil, rivastigmine, galantamine) work on one system; memantine works on a different one. In moderate to severe disease, they're often combined.

Will it help my parent? Modestly, if it helps at all. Expect a slower rate of decline rather than a rebound. Some people also see less agitation or better engagement.

Why is it better tolerated than donepezil? Different mechanism. Memantine doesn't ramp up cholinergic signaling, so it doesn't cause the nausea, diarrhea, and heart-rate slowing that the cholinesterase inhibitors do.

Do we need both? Often, yes, in moderate to severe disease. The combination is more effective than either alone for many people, and the tolerability of adding memantine to a cholinesterase inhibitor is usually fine.

Does the kidney function matter? Yes. If kidney function is reduced, the dose has to come down or side effects (dizziness, confusion) become more likely.

Questions to ask your prescriber

• What are we hoping this will do, and how will we know?
• Given the kidney function, is the dose right?
• Should we combine memantine with the current cholinesterase inhibitor?
• What signs would tell us it isn't the right medication?
• When would we consider stopping it?

Sources

This guide draws on current prescribing information and public health references. It is reviewed for clinical accuracy and updated as guidance changes, and current as of June 8, 2026.

• U.S. Food and Drug Administration. Memantine (Namenda) prescribing information.
• DailyMed, U.S. National Library of Medicine. Memantine label.
• MedlinePlus, U.S. National Library of Medicine. Memantine.
• National Institute of Mental Health. Mental health medications.
• American Academy of Neurology. Practice guideline update on pharmacologic treatment of dementia.
• American Psychiatric Association. Practice guideline on the use of antipsychotics and cognitive enhancers in dementia.