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Memantine (Ebixa)

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist PBS listed for use in moderate to severe Alzheimer’s disease. Its action is distinct from its cholinergic counterparts, acting as a neuroprotective agent by antagonising the excitatory effects of glutamate and preventing excitotoxicity.

Memantine is recommended as an option for people with moderate-to-severe Alzheimer's disease who are intolerant of or have a contraindication to acetylcholinesterase inhibitors.

For people with severe renal impairment (creatinine clearance < 30ml/min) the dose of memantine should be halved

When to prescribe

Clinical criteria for initiating treatment with memantine is as follows:

  1. Patient must have a baseline sMMSE score of 10-14
  2. The diagnosis must be confirmed by, or in consultation with a specialist / consultant physician (including psychiatrist)
  3. The treatment must be the sole PBS subsidized therapy for this condition. It is important to note that some benefits have been associated with combined therapy with an acetylcholinesterase inhibitor, however this is NOT PBS listed.

For patients with a sMMSE score of 9 or less, see acetylcholinesterase inhibitor criteria.

Precautions before commencing

Precautions

  • History of seizures – contraindicated
  • As memantine is renally cleared, reduce dose in renal impairment if CrCl <30ml/minute

Adverse effects

  • Common (>1%) – confusion, dizziness, drowsiness, headache, insomnia, agitation, hallucinations, dyspnoea, hypersensitivity
  • Infrequent – vomiting, anxiety, hypertonia, VTE
  • Rare – seizure, rash, renal failure, cholestatic hepatitis, heart failure, bradycardia

Dosing

Memantine orally (Ebixa)

  1. Initially 5mg daily in the morning for the first week, 5mg twice daily in the second week, 10mg daily in the morning plus 5mg at dinnertime in the third week.
  2. Maintenance dose thereafter is 10mg twice daily.

Continuing treatment

Clinical criteria for continuing treatment are as follows:

  1. Patient must have received six months of sole PBS-subsidised initial therapy with this drug
  2. Patient must demonstrate a clinically meaningful response to the initial treatment between 3-6 months
  3. Treatment must be the sole PBS subsidised therapy for this condition

Prior to continuing treatment, assess response by re-assessing cognitive, functional and behavioural responses. A repeat sMMSE and history from the patient, the patient’s family, or carer should be documented. The GP should use this information to establish agreement that treatment is continuing to produce worthwhile benefit.

Treatment should cease if there is no agreement of benefit as there is always the possibility of harm from unnecessary use.

Re-assessments for a clinically meaningful response are to be undertaken and documented every six months.

Clinically meaningful response to treatment is demonstrated in the following areas:

  • The stabilisation, lack of significant decline, or slowing of decline
  • Patient's quality of life including but not limited to level of independence and happiness
  • Patient's cognitive function including but not limited to memory, recognition and interest in environment
  • Patient's behavioural symptoms, including but not limited to hallucination, delusions, anxiety, marked agitation or associated aggressive behaviour
  • Also consider the patients family’s perception of ongoing benefit

Clinical Practice Guidelines for Dementia in Australia: Recommendations 2016