Memantine: what it treats, how to take it, side effects
Last updated September 3, 2026.
Memantine is an NMDA receptor antagonist - it decreases abnormal activity in the brain. You may know it as Namenda. Same honest framing as every dementia drug: it may improve thinking and memory or slow their loss in Alzheimer's disease, but it does not cure the disease or stop the eventual decline.
What does it treat?
The symptoms of Alzheimer's disease. It is often added when the disease has moved past the mild stage, alone or alongside a cholinesterase inhibitor. The goal is function held longer, not function restored.
How do you take it?
Tablet or liquid once or twice a day; extended-release capsule once a day - with or without food, same time(s) daily. Your doctor starts low and increases no more than once a week. Swallow extended-release capsules whole, or open one and sprinkle the contents on a spoonful of applesauce - swallowed immediately, never chewed, never saved. The oral solution comes with its own syringe: squirt slowly into a corner of the mouth, never mix with other liquids. Keep taking it even when things seem stable - stable is the treatment working. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: dizziness, confusion, aggression, depression, headache, sleepiness, diarrhea, constipation, nausea, vomiting, weight gain, pain anywhere in the body especially the back, and cough.
- Serious - call your doctor immediately or get emergency help: shortness of breath, and hallucinations - seeing things or hearing voices that do not exist.
Who should not take it?
Flag kidney disease before starting - the drug clears through the kidneys and dosing changes when they slow. Report every other medication. For caregivers: the pill organizer is the safety system, because the condition being treated is memory loss.
When is it an emergency?
New shortness of breath, or hallucinations the person cannot be talked through, warrant same-day urgent care. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
Will memantine bring my parent back?
No - and the honest framing is on the MedlinePlus page: it may improve the ability to think and remember or slow the loss of those abilities, but it will not cure Alzheimer's or prevent the eventual loss. What families actually report is softer but real: less agitation, more settled evenings, longer stretches of recognition. Those gains are the treatment working.
Why is memantine often added to donepezil?
Different mechanisms, different stages. The cholinesterase inhibitors - donepezil and family - boost a brain chemical that memory runs on; memantine calms a different, overactive pathway. In moderate-to-severe disease they are often paired because the two levers can each hold a little more function. The combination is routine, evidence-backed, and prescribed deliberately, not accidentally.
Why did the dose increase only once a week at the start?
Because dizziness and confusion - already fragile territory in dementia - are the main side effects, and weekly steps let each change declare itself before the next one lands. MedlinePlus: your doctor starts low and increases no more than once every week. The slow build is the tolerability strategy, not a delay.
My mother seems more confused some days. Is it the drug?
Confusion is on the common-effects list - so it could be - but dementia itself fluctuates, infections mimic confusion, and other medications pile on. The answer is a log: note the days, the timing against doses, and anything new in her routine, and bring it to the prescriber. Hallucinations or new shortness of breath skip the log - those are call-immediately items.
Why did the doctor ask about my father's kidneys?
Memantine leaves the body through the kidneys, and slow kidneys let it accumulate - more dizziness, more confusion. Kidney disease is a before-you-start flag and dosing adjusts around it. Any new swelling, fatigue, or urine changes on the drug are worth reporting for the same reason.
What happens if a dose of memantine is missed?
Give it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. A caregiver-filled weekly pill organizer is the real answer to this question: it turns "did he take it?" into something you can check instead of guess.