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NMDA receptor antagonist Pregnancy: Memantine should not be used during pregnancy unless clearly necessary. There are no or limited data in pregnant women, and animal studies indicate a potential for reducing intrauterine growth at exposure levels identical to or slightly higher than human exposure. Women taking memantine should not breast-feed (excretion into human milk is not known but probable given the lipophilicity of the substance).

Memantine hydrochloride

Brand names: Ebixa

Used in: Delirium & Cognitive Impairment

Memantine hydrochloride is an NMDA receptor antagonist used for moderate to severe Alzheimer's disease.

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: 5 mg once daily in week 1 (days 1 to 7), 10 mg once daily in week 2 (days 8 to 14), 15 mg once daily in week 3 (days 15 to 21), then a maintenance dose of 20 mg once daily from week 4 onwards
Route: Oral — tablets may be taken with or without food
Frequency: Once a day, at the same time every day
Max: 20 mg per day
UK SPC (Memantine Hydrochloride 10 mg film-coated tablets, eMC product 101171), Alzheimer's dementia. 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. The maintenance dose is reached by upward titration of 5 mg per week over the first 3 weeks to reduce the risk of undesirable effects; the titration steps are given in the SPC as half a 10 mg tablet, one 10 mg tablet, one and a half 10 mg tablets, then two 10 mg tablets (or one 20 mg tablet). Tolerance and dosing should be reassessed regularly, preferably within three months of starting; discontinuation should be considered when a therapeutic effect is no longer evident or the patient does not tolerate treatment. Elderly: on the basis of the clinical studies, the recommended dose for patients over 65 years is 20 mg per day, as described above. Hepatic impairment: no dose adjustment in mild or moderate impairment (Child-Pugh A and B); no data in severe hepatic impairment and administration is not recommended. Paediatric population: no data available. (US label, cross-check: starting dose 5 mg once daily, increased in 5 mg increments to 10 mg/day given as 5 mg twice daily, then 15 mg/day, then 20 mg/day given as 10 mg twice daily, with a minimum interval of one week between increases; if the patient fails to take memantine for several days, dosing may need to be resumed at lower doses and retitrated.)

Dose adjustments

Renal

Creatinine clearance 50 to 80 ml/min (mild impairment): no dose adjustment required. Creatinine clearance 30 to 49 ml/min (moderate impairment): 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 to 29 ml/min (severe impairment): daily dose should be 10 mg per day. (US label: a target dose of 5 mg twice daily is recommended in severe renal impairment, creatinine clearance 5 to 29 ml/min by Cockcroft-Gault.)

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.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients

Side effects

  • Dizziness (common; 6.3% versus 5.6% placebo)
  • Headache (common; 5.2% versus 3.9% placebo)
  • Constipation (common; 4.6% versus 2.6% placebo)
  • Hypertension (common; 4.1% versus 2.8% placebo)
  • Somnolence (common; 3.4% versus 2.2% placebo)
  • Also common: balance disorders, dyspnoea, drug hypersensitivity, elevated liver function tests, fatigue; uncommon: confusion, hallucinations (mainly in severe Alzheimer's disease), cardiac failure, venous thrombosis/thromboembolism; very rare: seizures

Interactions

  • Drugs and conditions that make the urine alkaline (e.g. carbonic anhydrase inhibitors, sodium bicarbonate; also renal tubular acidosis or severe urinary tract infection) — memantine clearance is reduced by about 80% at urine pH 8, risking accumulation and increased adverse effects; use with caution (US label)
  • Other NMDA antagonists — amantadine, ketamine and dextromethorphan; combined use has not been systematically evaluated and should be approached with caution (US label)

Clinical monograph

How it works

It provides voltage-dependent, non-competitive blockade of the NMDA glutamate receptor, attenuating pathological glutamatergic activity while preserving physiological signalling.

Prescribing in practice

  • The dose must be reduced in moderate to severe renal impairment because elimination depends on renal function and is reduced when urine is alkaline.
  • Use with caution in epilepsy and in patients with a history of seizures, and review concurrent NMDA-acting drugs such as ketamine and amantadine.
  • Titrate the dose upward gradually to improve tolerability.

Monitoring

Monitor renal function, cognitive and functional response and tolerability including dizziness, confusion and headache.

Counselling the patient

  • It can be taken with or without food, ideally at a consistent time each day.
  • Report dizziness, confusion or new seizures.
  • Carers should continue regular review of benefit and overall function.

Evidence & guidelines

NICE recommends memantine as an option for managing moderate to severe Alzheimer's disease.

Reference: NICE TA217/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).

Related

Curated clinical cross-links plus same-class fallbacks.

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