Memantine

NMDA Receptor Antagonist·Neurology - Anti-Parkinson & Cognitive

Moderate to severe Alzheimer's disease

Authority requiredPBSCOGNITIVEEbixa10 mg tablet+2

Max Dose

20 mg/day

Half-life

60-100 h

Renal Adj.

MANDATORY

Agitation

RISK

Rapid Summary

Overview

NMDA receptor antagonist. Protects neurons from glutamate excitotoxicity. Used for moderate-to-severe Alzheimer's, often layered on top of Donepezil.

Maximum Dose

Max 20 mg/day.

Clinical Focus

Unlike Donepezil, it relies entirely on the kidneys for clearance and does not cause bradycardia or GI upset.

Bottom Line

Memantine is the NMDA antagonist for moderate-severe Alzheimer's disease (alone or with donepezil), but provides only modest benefit and can cause dizziness, headache, and confusion.

Formulation & Access

Brand Names

Ebixa

Oral Routes

Tablets (10 mg, 20 mg). Oral liquid/drops.

Prescribing & PBS

Authority Required (PBS).

Indications & Use

Primary

PBSTGA

Moderate to severe Alzheimer's disease.

Clinical Place

Used when Alzheimer's progresses beyond the mild stage. Often used in combination with Donepezil for additive benefits.

Quick reference

Class & Role

NMDA Receptor Antagonist — NMDA receptor antagonist.

Route / Formulation

Tablets (10 mg, 20 mg). Oral liquid/drops. (Ebixa)

Usual Dose & Max

Week 1: PO 5 mg OD. Week 2: 10 mg. Week 3: 15 mg. Week 4: 20 mg OD. Max 20 mg/day.

Key Indication Doses

Alzheimer's Disease: Week 1: PO 5 mg OD. Week 2: 10 mg. Week 3: 15 mg. Week 4: 20 mg OD. Renal Impairment: If eGFR 30-49, Max 10 mg/day. If eGFR < 30, avoid or strictly limit to 5 mg/day.

Best Uses

Memantine is the NMDA antagonist for moderate-severe Alzheimer's disease (alone or with donepezil), but provides only modest benefit and can cause dizziness, headache, and confusion.

Avoid / Cautions

Severe renal failure (accumulation causes intense neurotoxicity).

Key Risks

Neurological: Dizziness, confusion, headache. Somnolence or paradoxical agitation. Cardiovascular: Hypertension. Gastrointestinal: Constipation (Notice it causes constipation, whereas Donepezil causes diarrhea).

Key Interactions

Other NMDA antagonists (Amantadine, Ketamine, Dextromethorphan). Avoid combination due to risk of pharmacotoxic psychosis. Very clean metabolic profile (no CYP interactions).

Monitoring

Baseline and routine U&E and eGFR to guide safe dosing limits. Monitor for worsening confusion or agitation during the initial 4-week titration phase.

Clinical Pearl

Because Donepezil and Memantine have completely different mechanisms (boosting ACh vs blocking Glutamate) and opposite side effects (diarrhea vs constipation), combining them in severe Alzheimer's is highly logical and often cancels out the GI side effects.

Access

Authority requiredEbixa10 mg tablet

Brand: Ebixa
PBS status: Authority required
Formulation: Tablets (10 mg, 20 mg)

Memantine

NMDA Receptor Antagonist·Neurology - Anti-Parkinson & Cognitive

Moderate to severe Alzheimer's disease

Authority requiredPBSCOGNITIVEEbixa10 mg tablet+2

Max Dose

20 mg/day

Half-life

60-100 h

Renal Adj.

MANDATORY

Agitation

RISK

Rapid Summary

Overview

NMDA receptor antagonist. Protects neurons from glutamate excitotoxicity. Used for moderate-to-severe Alzheimer's, often layered on top of Donepezil.

Maximum Dose

Max 20 mg/day.

Clinical Focus

Unlike Donepezil, it relies entirely on the kidneys for clearance and does not cause bradycardia or GI upset.

Bottom Line

Memantine is the NMDA antagonist for moderate-severe Alzheimer's disease (alone or with donepezil), but provides only modest benefit and can cause dizziness, headache, and confusion.

Formulation & Access

Brand Names

Ebixa

Oral Routes

Tablets (10 mg, 20 mg). Oral liquid/drops.

Prescribing & PBS

Authority Required (PBS).

Indications & Use

Primary

PBSTGA

Moderate to severe Alzheimer's disease.

Clinical Place

Used when Alzheimer's progresses beyond the mild stage. Often used in combination with Donepezil for additive benefits.

Quick reference

Class & Role

NMDA Receptor Antagonist — NMDA receptor antagonist.

Route / Formulation

Tablets (10 mg, 20 mg). Oral liquid/drops. (Ebixa)

Usual Dose & Max

Week 1: PO 5 mg OD. Week 2: 10 mg. Week 3: 15 mg. Week 4: 20 mg OD. Max 20 mg/day.

Key Indication Doses

Alzheimer's Disease: Week 1: PO 5 mg OD. Week 2: 10 mg. Week 3: 15 mg. Week 4: 20 mg OD. Renal Impairment: If eGFR 30-49, Max 10 mg/day. If eGFR < 30, avoid or strictly limit to 5 mg/day.

Best Uses

Memantine is the NMDA antagonist for moderate-severe Alzheimer's disease (alone or with donepezil), but provides only modest benefit and can cause dizziness, headache, and confusion.

Avoid / Cautions

Severe renal failure (accumulation causes intense neurotoxicity).

Key Risks

Key Interactions

Other NMDA antagonists (Amantadine, Ketamine, Dextromethorphan). Avoid combination due to risk of pharmacotoxic psychosis. Very clean metabolic profile (no CYP interactions).

Monitoring

Baseline and routine U&E and eGFR to guide safe dosing limits. Monitor for worsening confusion or agitation during the initial 4-week titration phase.

Clinical Pearl

Access

Authority requiredEbixa10 mg tablet

Brand: Ebixa
PBS status: Authority required
Formulation: Tablets (10 mg, 20 mg)