Treatment of moderate to severe dementia of the Alzheimer type.
Also known as: Axura, Ebixa
DailyMed approved label (Memantine Hydrochloride Tablet; setID cbfd9d95-f50b-45ff-9857-9f1712c45e56).
DailyMed approved label (Memantine Hydrochloride Tablet; setID cbfd9d95-f50b-45ff-9857-9f1712c45e56).
Memantine + dextromethorphan: NMDA antagonists in combination — use with caution.
The FDA memantine label documents: "Use with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution" (section 7.1). Dextromethorphan, an antitussive, is a low-affinity NMDA antagonist; combining with memantine, a moderate-affinity NMDA antagonist, may potentiate CNS adverse effects — sedation, confusion, dizziness and, in extreme cases, hallucinations. The combination is possible in dementia patients using antitussives, but should be avoided or used with caution. The practical guidance is to monitor mental status changes and sedation; if symptoms occur, reduce or stop one of the drugs.
Memantine + dextromethorphan: NMDA antagonists in combination — use with caution.
The FDA memantine label documents: "Use with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution" (7.1). Dextromethorphan and memantine are both NMDA antagonists — the combination may potentiate CNS adverse effects.
Monitor mental status changes and sedation.
Excessive sedation, confusion or hallucinations with the combination.
Use with caution; monitor sedation, confusion and CNS effects in the combination.
DailyMed/FDA (NIH/NLM) — approved Memantine label (NAMENDA XR), section 7.1: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=617dcd31-3215-4dd8-9b6e-d888d3bf30f3 ; approved Dextromethorphan label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0d99237c-0b52-0af6-e063-6394a90aba14
Memantine + ketamine: NMDA antagonists in combination — use with caution (possible profound sedation).
The FDA memantine label documents that the combination with other NMDA antagonists (including ketamine) has not been systematically evaluated and should be approached with caution (section 7.1). Ketamine is a potent NMDA antagonist, used in anaesthesia and increasingly in low doses for resistant depression and chronic pain; the additive NMDA antagonism with memantine may potentiate dissociative effects, profound sedation and psychomotor impairment. The interaction is relevant mainly in the perioperative or therapeutic ketamine setting in patients on memantine (Alzheimer dementia). The practical guidance is to inform the anaesthetic team of current medication, monitor level of consciousness and vital signs, and adjust ketamine doses accordingly.
Memantine + ketamine: NMDA antagonists in combination — use with caution (possible profound sedation).
The FDA memantine label documents: "Use with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution" (7.1). Ketamine is a potent NMDA antagonist — combining with memantine may potentiate dissociative and sedative effects.
Monitor level of consciousness and vital signs in the perioperative setting.
Prolonged sedation, dissociation or hypertension with the combination.
Use with caution; monitor sedation, dissociation and blood pressure in the combination (anaesthetic setting).
DailyMed/FDA (NIH/NLM) — approved Memantine label (NAMENDA XR), section 7.1: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=617dcd31-3215-4dd8-9b6e-d888d3bf30f3 ; approved Ketamine label (KETALAR): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=14e8f864-8b8a-4e7e-8439-e510d3107063
Memantine + amantadine: NMDA antagonists in combination — use with caution.
The FDA memantine label documents that the combination with other NMDA antagonists (amantadine, ketamine, dextromethorphan) should be avoided (section 7.1), given the risk of additive effects on the glutamatergic system. Memantine is a moderate-affinity NMDA antagonist used in Alzheimer disease; amantadine is a weak non-competitive NMDA antagonist used in Parkinson disease — the sum of the two may potentiate central adverse effects such as confusion, hallucinations, drowsiness and psychomotor impairment. The combination is possible in patients with overlapping dementia and Parkinson, but should be avoided or used with active monitoring. In the presence of signs of central toxicity, reduce or stop one of the drugs.
Memantine + amantadine: additive NMDA antagonism — avoid the combination (risk of central toxicity).
The FDA memantine label documents: "Use with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution" (7.1). Amantadine, used in Parkinson disease, shares NMDA antagonism with memantine — possible additive CNS effects.
Monitor mental status changes and extrapyramidal effects.
Confusion, hallucinations or worsening of parkinsonian symptoms with the combination.
Use with caution; monitor confusion, hallucinations and CNS effects in the combination.
DailyMed/FDA (NIH/NLM) — approved Memantine label (section 7.1): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3350f7d-2e51-4e1a-a6d0-c4f87ea99a56 ; approved Amantadine label (GOCOVRI): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2bee0631-0028-1314-e063-6394a90aaaed
Memantine + warfarin: memantine may potentiate the anticoagulant effect of warfarin — monitor INR.
The Prontuário Terapêutico documents in the memantine monograph the possibility of potentiating the anticoagulant effect of warfarin. The mechanism is not fully clarified, but the interaction is clinically relevant because dementia patients (memantine indication) are frequently elderly and polymedicated, including anticoagulated. The risk is warfarin over-anticoagulation with supratherapeutic INR and bleeding (bruising, gum bleeding, melaena) when memantine is started or adjusted. The practical guidance is to monitor INR after starting, adjusting or stopping memantine in patients anticoagulated with warfarin, and watch for bleeding signs; the same precaution applies to the new oral anticoagulants, although less documented.
Memantine + warfarin: memantine may potentiate the anticoagulant effect of warfarin — monitor INR.
The Prontuário Terapêutico documents in the memantine monograph: "Possibility of potentiating the anticoagulant effect of warfarin". The mechanism is not fully clarified — INR monitoring is recommended when the combination is started or changed.
Watch for bleeding signs (bruising, gum bleeding, melaena).
INR above target range or bleeding with the combination.
Monitor INR after starting, adjusting or stopping memantine in patients anticoagulated with warfarin.
Prontuário Terapêutico do INFARMED (11th ed., 2012) — Memantine ; approved Warfarin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=541c9a70-adaf-4ef3-94ba-ad4e70dfa057
Drastic dietary changes may alkalinise the urine and alter memantine elimination.
Avoid drastic dietary changes; monitor conditions that alter urine pH.
EMC-UK (MHRA) — approved Ebixa (Memantine) SmPC: https://www.medicines.org.uk/emc/product/8222/smpc
Memantine may lower the convulsion threshold.
Use with caution in patients with epilepsy or a history of seizures.
EMC-UK (MHRA) — approved Ebixa (Memantine) SmPC: https://www.medicines.org.uk/emc/product/8222/smpc
Limited data; safety in pregnancy is unknown.
Not recommended during pregnancy.
Excreted in milk; avoid while breastfeeding.
Advise effective contraception.
EMC-UK (MHRA) — approved Ebixa (Memantine) SmPC: https://www.medicines.org.uk/emc/product/8222/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Low to moderate affinity NMDA antagonist: persistent activation of central NMDA receptors by glutamate contributes to Alzheimer symptomatology; memantine modulates this excitotoxicity without interfering with physiological synaptic transmission.
Uncompetitive (open-channel) antagonism of NMDA receptors, with low to moderate affinity, binding preferentially to the receptor-operated cation channels; no evidence of preventing or slowing neurodegeneration.
Oral bioavailability of ~100%; plasma peaks at 3–8 hours; absorption is not affected by food.
Minimal hepatic metabolism (no active metabolites); excretion is predominantly renal, unchanged (~50%) and as metabolites.
Elimination half-life of ~60–80 hours (increased in renal impairment and slightly in hepatic impairment).
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
