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NMDA receptor antagonist — dementia Pregnancy: Not applicable.

Memantine

Brand names: Ebixa, Maruxa

Adult dose

Dose: 5 mg once daily (week 1), increasing by 5 mg/week to 20 mg/day
Route: Oral
Frequency: Once daily
Max: 20 mg/day
Moderate-severe Alzheimer's disease: start 5 mg OD, increase by 5 mg every week: 10 mg OD (week 2), 15 mg OD (week 3), 20 mg OD (week 4 onwards). Can be combined with AChEI. NICE TA217: memantine licensed for moderate-severe AD or when AChEI not tolerated.

Paediatric dose

Route: Not applicable
Frequency: Not licensed in children
Max: Not applicable
Not licensed in children.

Dose adjustments

Renal

Reduce to 10 mg/day if eGFR 5–29 mL/min.

Hepatic

Use with caution in severe hepatic impairment.

Clinical pearls

  • Alternative to AChEI in moderate-severe AD or useful add-on
  • Generally well-tolerated — no GI cholinergic side effects unlike AChEIs
  • Oral solution available for patients with dysphagia
  • Review at 3–6 months; continue if clinical benefit
  • Urinary alkalinisers (e.g., potassium citrate, acetazolamide) reduce memantine excretion — risk of toxicity

Contraindications

  • Hypersensitivity to memantine
  • Renal tubular acidosis
  • Urinary tract infections causing alkaline urine (accumulation)

Side effects

  • Dizziness and headache
  • Constipation
  • Hypertension
  • Somnolence
  • Confusion (paradoxical — discontinue if worsening confusion)

Interactions

  • Amantadine, ketamine — increased CNS toxicity
  • NMDA antagonists — additive effects
  • Dopaminergic drugs — enhanced dopaminergic effects

Monitoring

  • MMSE/MoCA
  • Blood pressure
  • Renal function

Reference: BNFc; BNF; NICE TA217; NICE NG97. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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