NMDA Receptor Antagonist — Dementia Pregnancy: Avoid — insufficient data

Memantine

Brand names: Ebixa, Namenda

Adult dose

Dose: 5 mg once daily initially; increase by 5 mg weekly; maintenance 20 mg once daily

Route: Oral

Frequency: Once daily

Max: 20 mg/day

NMDA glutamate receptor antagonist — reduces excitotoxicity in Alzheimer's disease. Licensed for moderate–severe Alzheimer's dementia. Can be used alone or with cholinesterase inhibitors (donepezil/rivastigmine/galantamine). Less benefit in mild disease.

Paediatric dose

Route:

Seek specialist opinion — studied in autism spectrum disorder in research settings; not licensed in children.

Dose adjustments

Renal

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

Hepatic

Avoid in severe hepatic impairment.

Clinical pearls

NICE NG97: memantine is first-line for moderate–severe Alzheimer's (MMSE ≤20) or in patients who cannot tolerate cholinesterase inhibitors
Combination of memantine + donepezil shows modest additional benefit vs. donepezil alone in moderate–severe AD
Mechanism differs from cholinesterase inhibitors — complementary mechanisms allow combination therapy

Contraindications

Hypersensitivity to memantine

Side effects

Dizziness
Headache
Constipation
Confusion (paradoxically — in dementia patients)
Hypertension
Somnolence

Interactions

Dextromethorphan (additive NMDA antagonism — caution)
Amantadine (both NMDA antagonists — additive psychotic reactions)
L-DOPA (may increase dopaminergic effects)
Urinary alkalinisers (reduce memantine excretion — increase levels)

Monitoring

Cognitive assessment (MMSE or MoCA) every 6 months
Functional status (ADLs)
Carer burden assessment

Reference: BNFc; BNF 90; NICE NG97 (Dementia); Cochrane Review on Memantine; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Memantine · NMDA receptor antagonist — dementia

Pathways