NMDA receptor antagonist — dementia Pregnancy: There are no or limited data from use in pregnant women; animal studies indicate a potential for reducing intrauterine growth. Memantine should not be used during pregnancy unless clearly necessary. It is not known whether memantine is excreted in human breast milk but this probably occurs — women taking memantine should not breast-feed.

Memantine

Brand names: Ebixa, Maruxa

Used in: Delirium & Cognitive Impairment

Memantine is used for moderate-to-severe Alzheimer's disease, alone or sometimes with an acetylcholinesterase inhibitor.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Maintenance dose 20 mg per day, reached by upward titration of 5 mg per week over the first 3 weeks (week 1: 5 mg/day; week 2: 10 mg/day; week 3: 15 mg/day; from week 4 onwards: 20 mg/day)

Route: Oral (film-coated tablets, with or without food)

Frequency: Once a day, taken at the same time every day

Max: 20 mg per day

Treatment should be initiated and supervised by a physician experienced in the diagnosis and treatment of Alzheimer's dementia, and should only be started if a caregiver is available who will regularly monitor intake. Tolerance and dosing should be reassessed regularly, preferably within three months of starting, and thereafter the clinical benefit and tolerance reassessed regularly. Discontinuation should be considered when evidence of a therapeutic effect is no longer present or if the patient does not tolerate treatment. Elderly: on the basis of the clinical studies, the recommended dose for patients over the age of 65 years is 20 mg per day, titrated as above. Hepatic impairment: no dose adjustment in mild or moderate impairment (Child-Pugh A and B); not recommended in severe hepatic impairment (no data). Caution is recommended in patients with epilepsy, a former history of convulsions, or predisposing factors for epilepsy. Factors that raise urine pH (drastic dietary change, massive ingestion of alkalising gastric buffers, renal tubular acidosis, severe urinary tract infections with Proteus) may necessitate careful monitoring. Paediatric population: no data available.

Dose adjustments

Renal

Creatinine clearance 50-80 mL/min: no dose adjustment required. Creatinine clearance 30-49 mL/min: daily dose should be 10 mg per day; if well tolerated after at least 7 days of treatment, the dose could be increased up to 20 mg/day according to the standard titration scheme. Creatinine clearance 5-29 mL/min: daily dose should be 10 mg per day.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

The recommended starting dose of memantine hydrochloride tablets is 5 mg once daily. The dose should be increased in 5 mg increments to 10 mg/day (5 mg twice daily), 15 mg/day (5 mg and 10 mg as separate doses), and 20 mg/day (10 mg twice daily). The minimum recommended interval between dose increases is one week. The dosage shown to be effective in controlled clinical trials is 20 mg/day. Memantine hydrochloride tablets can be taken with or without food. If a patient misses a single dose of memantine hydrochloride tablets, that patient should not double up on the next dose. The next dose should be taken as scheduled. If a patient fails to take memantine hydrochloride tablets for several …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2023-08-17. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Dizziness (6.3% vs 5.6% placebo)
Headache (5.2% vs 3.9%)
Constipation (4.6% vs 2.6%)
Somnolence (3.4% vs 2.2%)
Hypertension (4.1% vs 2.8%)

Interactions

L-dopa, dopaminergic agonists and anticholinergics — their effects may be enhanced by concomitant treatment with NMDA-antagonists such as memantine
Barbiturates and neuroleptics — their effects may be reduced
Dantrolene or baclofen — concomitant administration can modify their effects and a dose adjustment may be necessary
Amantadine — concomitant use should be avoided owing to the risk of pharmacotoxic psychosis; the same may be true for ketamine and dextromethorphan
Phenytoin — one published case report of a possible risk with the combination
Cimetidine, ranitidine, procainamide, quinidine, quinine and nicotine — use the same renal cationic transport system and may interact, with a potential risk of increased plasma levels
Hydrochlorothiazide — there may be a possibility of a reduced serum level of hydrochlorothiazide when co-administered with memantine
Isolated post-marketing cases of increased international normalised ratio (INR) have been reported

Clinical monograph

How it works

It is a moderate-affinity NMDA-receptor antagonist that reduces glutamate-mediated excitotoxicity while preserving physiological signalling.

Prescribing in practice

It is generally well tolerated, with a different side-effect profile from acetylcholinesterase inhibitors (fewer cholinergic effects).
Reduce the dose in significant renal impairment.
Dizziness, headache and constipation can occur; titrate the dose upward gradually.

Monitoring

Review cognition, function and tolerability; check renal function where relevant.

Counselling the patient

The dose is increased gradually at the start.
Report persistent dizziness or confusion.
It manages symptoms rather than curing the condition.

Evidence & guidelines

Recommended for moderate-to-severe Alzheimer's disease per NICE NG97/TA217.

Reference: NICE TA217; NICE NG97; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Memantine · NMDA Receptor Antagonist — Dementia

Pathways