| Item |
Information |
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Drug Groups
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approved; investigational |
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Description
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Memantine is an amantadine derivative with low to moderate-affinity for NMDA receptors. It is a noncompetitive NMDA receptor antagonist that binds preferentially to NMDA receptor-operated cation channels. It blocks the effects of excessive levels of glutamate that may lead to neuronal dysfunction. It is under investigation for the treatment of Alzheimer's disease, but there has been no clinical support for the prevention or slowing of disease progression. |
| Indication |
For the treatment of moderate to severe dementia of the Alzheimer's type. |
| Pharmacology |
Memantine, an amantadine derivative, is an NMDA receptor antagonist used in the treatment of Alzheimer's disease. It differs from traditional agents used in Alzheimer's disease by acting on glutamatergic neurotransmission, rather than cholinergic. There is some evidence that dysfunction of glutamatergic neurotransmission, manifested as neuronal excitotoxicity, is involved in the aetiology of Alzheimer's disease (Cacabelos et al., 1999). As such, targeting the glutamatergic system, specifically NMDA receptors, was a novel approach to treatment in view of the limited efficacy of existing drugs targeting the cholinergic system. A systematic review of randomised controlled trials found that memantine has a positive effect on cognition, mood, behaviour, and the ability to perform daily activities. There is no evidence that memantine prevents or slows neurodegeneration in patients with Alzheimer's disease. |
| Toxicity |
Side effects include pain, abnormal crying, leg pain, fever, increased apetite. Adverse drug reactions include: dizziness, confusion, headache, hallucinations, tiredness. Less common side effects include: vomiting, anxiety, hypertonia, cystitis, and increased libido. Doses of up to 400 mg have been tolerated. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
Excreted largely unchanged. About 20% is metabolized to 1-amino-3-hydroxymethyl-5-methyl-adamantane and 3-amino-1-hydroxy-5,7-dimethyl-adamantane. |
| Absorption |
Well absorbed orally with a bioavailability of approximately 100%. Peak plasma concentrations are reached in 3-7 hours. Food has no effect on absorption. |
| Half Life |
60-100 hours |
| Protein Binding |
45% |
| Elimination |
Memantine undergoes partial hepatic metabolism. About 48% of administered drug is excreted unchanged in urine; the remainder is converted primarily to three polar metabolites which possess minimal NMDA receptor antagonistic activity: the N-glucuronide conjugate, 6-hydroxy memantine, and 1-nitroso-deaminated memantine. It is excreted predominantly in the urine, unchanged. |
| Distribution |
* 9 to 11 L/kg |
| References |
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Cacabelos R, Takeda M, Winblad B: The glutamatergic system and neurodegeneration in dementia: preventive strategies in Alzheimer's disease. Int J Geriatr Psychiatry. 1999 Jan;14(1):3-47.
[Pubmed]
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| • |
Rogawski MA, Wenk GL: The neuropharmacological basis for the use of memantine in the treatment of Alzheimer's disease. CNS Drug Rev. 2003 Fall;9(3):275-308.
[Pubmed]
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Robinson DM, Keating GM: Memantine: a review of its use in Alzheimer's disease. Drugs. 2006;66(11):1515-34.
[Pubmed]
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Rogawski MA: Low affinity channel blocking (uncompetitive) NMDA receptor antagonists as therapeutic agents--toward an understanding of their favorable tolerability. Amino Acids. 2000;19(1):133-49.
[Pubmed]
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Rammes G, Rupprecht R, Ferrari U, Zieglgansberger W, Parsons CG: The N-methyl-D-aspartate receptor channel blockers memantine, MRZ 2/579 and other amino-alkyl-cyclohexanes antagonise 5-HT(3) receptor currents in cultured HEK-293 and N1E-115 cell systems in a non-competitive manner. Neurosci Lett. 2001 Jun 22;306(1-2):81-4.
[Pubmed]
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