Memantine

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Memantine
Memantine.svg
Memantine-3d-sticks.png
Systematic (IUPAC) name
3,5-dimethyltricyclo[3.3.1.13,7]decan-1amine
or
3,5-dimethyladamantan-1-amine
Clinical data
Trade names Namenda
AHFS/Drugs.com monograph
MedlinePlus a604006
Licence data EMA:Link, US FDA:link
Pregnancy cat.
Legal status
Routes Oral
Pharmacokinetic data
Bioavailability ~100%
Metabolism Hepatic (<10%)
Half-life 60–100 hours
Excretion Renal
Identifiers
CAS number 19982-08-2 YesY
ATC code N06DX01
PubChem CID 4054
DrugBank DB01043
ChemSpider 3914 YesY
UNII W8O17SJF3T YesY
KEGG D08174 YesY
ChEMBL CHEMBL807 YesY
Chemical data
Formula C12H21N 
Mol. mass 179.3 g/mol
 YesY (what is this?)  (verify)

Memantine is the first in a novel class of Alzheimer's disease medications acting on the glutamatergic system by blocking NMDA receptors. It was first synthesized by Eli Lilly and Company in 1968. Memantine is marketed under the brands Axura and Akatinol by Merz, Namenda by Forest, Ebixa and Abixa by Lundbeck and Memox by Unipharm. Memantine has been shown to have a modest effect in moderate-to-severe Alzheimer's disease[1] and in dementia with Lewy bodies.[2][3] Despite years of research, there is little evidence of effect on mild Alzheimer's disease.[4]

Medical use[edit]

Memantine is approved by the U.S. F.D.A and the European Medicines Agency for treatment of moderate-to-severe Alzheimer's disease,[5] and has now received a limited recommendation by the UK's National Institute for Health and Care Excellence for patients who fail other treatment options.[6] Within the new guidance memantine is recommended as an option for managing Alzheimer’s disease for people with: moderate Alzheimer’s disease who are intolerant of or have a contraindication to AChE (acetylcholinesterase) inhibitors or those with severe Alzheimer’s disease.

Memantine has been associated with a moderate decrease in clinical deterioration[7] with only a small positive effect on cognition, mood, behavior, and the ability to perform daily activities in moderate to severe Alzheimer's disease.[8] There does not appear to be any benefit in mild disease.[4]

Adverse effects[edit]

Memantine is, in general, well-tolerated.[8] Common adverse drug reactions (≥1% of patients) include confusion, dizziness, drowsiness, headache, insomnia, agitation, and/or hallucinations. Less common adverse effects include vomiting, anxiety, hypertonia, cystitis, and increased libido.[7][9] It has been reported to induce reversible neurological impairment in multiple sclerosis patients, which led to the halt of an ongoing clinical trial.[10][11] Though exceedingly rare, extrapyramidal side effects (such as dystonic reactions, etc.) may occur, in particular, in the younger population.[citation needed]

Like many other NMDA antagonists, memantine behaves as a dissociative anesthetic at supratherapeutic doses,[12] and has substituted for phencyclidine in rodent and primate drug discrimination studies.[13] Despite isolated reports, recreational use of memantine is rare due to the drug's long duration and limited availability.[12]

A recent study demonstrates therapeutically-relevant doses of memantine in the mouse can lead to disruption of cognitive flexibility.[14]

Biochemistry[edit]

The drug belongs to a class of drugs called NMDA receptor antagonists, which reduce certain types of brain activity by binding to NMDA receptors on brain cells and blocking the activity of the neurotransmitter glutamate. At normal levels, glutamate aids in memory and learning, but if levels are too high, glutamate appears to overstimulate nerve cells, killing them through excitotoxicity.

Pharmacology[edit]

Glutamatergic (NMDA receptor)[edit]

A dysfunction of glutamatergic neurotransmission, manifested as neuronal excitotoxicity, is hypothesized to be involved in the etiology of Alzheimer's disease. Targeting the glutamatergic system, specifically NMDA receptors, offers a novel approach to treatment in view of the limited efficacy of existing drugs targeting the cholinergic system.[15]

Memantine is a low-affinity voltage-dependent uncompetitive antagonist at glutamatergic NMDA receptors.[16][17][18][19][20] By binding to the NMDA receptor with a higher affinity than Mg2+ ions, memantine is able to inhibit the prolonged influx of Ca2+ ions, particularly from extrasynaptic receptors, which forms the basis of neuronal excitotoxicity. The low affinity, uncompetitive nature, and rapid off-rate kinetics of memantine at the level of the NMDA receptor-channel, however, preserves the function of the receptor at synapses, as it can still be activated by physiological release of glutamate following depolarization of the presynaptic neuron.[21][22][23][24][17][18][25][26][27] The interaction of memantine with NMDA receptors plays a major role in the symptomatic improvement that the drug produces in Alzheimer's disease. Moreover, there is no evidence as yet that the ability of memantine to protect against NMDA receptor-mediated excitotoxicity has a disease-modifying effect in Alzheimer's, although this has been suggested in animal models.[24]

Serotonergic (5-HT3 receptor)[edit]

Memantine acts as a non-competitive antagonist at the 5-HT3 receptor, with a potency similar to that for the NMDA receptor.[28] The clinical significance of this serotonergic activity in the treatment of Alzheimer's disease is unknown.

Cholinergic (nicotinic acetylcholine receptor)[edit]

Memantine acts as a non-competitive antagonist at different neuronal nicotinic acetylcholine receptors (nAChRs) at potencies possibly similar to the NMDA and 5-HT3 receptors, but this is difficult to ascertain with accuracy because of the rapid desensitization of nAChR responses in these experiments. It can be noted that memantine is an antagonist at alpha-7 nAChR, which may contribute to initial worsening of cognitive function during early memantine treatment. Alpha-7 nAChR upregulates quickly in response to antagonism, which could explain the cognitive-enhancing effects of chronic memantine treatment.[26][29][30] It has been shown that the number of nicotinic receptors in the brain are reduced in Alzheimer's disease, even in the absence of a general decrease in the number of neurons, and nicotinic receptor agonists are viewed as interesting targets for anti-Alzheimer drugs.[31] Consequently, this may also suggest that administration of nicotine itself may act against the effects of Alzheimer's disease. In fact a recent small double blind placebo controlled randomized trial published in the Journal Neurology demonstrated a significant benefit from use of 15 mg nicotine patches in non-smoking elderly patients with mild cognitive impairment. The small sample sizes suggest that the effect size is substantial due to the limited statistical power inherent in a small N trial. (see : http://www.ncbi.nlm.nih.gov/pubmed/22232050)

Dopaminergic (D2 receptor)[edit]

Memantine acts as an agonist at the dopamine D2 receptor.[32]

Availability[edit]

The hydrochloride (Memantine HCl) is white water soluble powder available as capsule-shaped film-coated tablets or oral solution. The tablets are available as 5 mg, 10 mg or 20 mg of memantine hydrochloride. The oral solution contains 2 mg of memantine hydrochloride per ml.

History[edit]

Memantine was first synthesized and patented by Eli Lilly and Company in 1968 (as cited in the Merck Index), and then developed by Merz in collaboration with Neurobiological Technologies, Inc. and Children's Hospital, Boston/Harvard Medical School, and then licensed to Forest for the U.S. and Lundbeck for selected European and international markets.

Sales of the drug reached $1.8 billion for 2010.[citation needed]

Research[edit]

Memantine is also being tested for generalized anxiety disorder, epilepsy, opioid dependence, systemic lupus erythematosus, depression, bipolar disorder,[33] obsessive compulsive disorder, Tourette Syndrome, problem gambling, attention-deficit hyperactivity disorder (ADHD),[34] glaucoma, tinnitus, neuropathic pain including Complex Regional Pain Syndrome,[35] pervasive developmental disorders, HIV associated dementia,[36] nystagmus,[37] multiple sclerosis,[10] autism,[38] migraine,[39] amyotrophic lateral sclerosis,[40] Down syndrome[41] and for protection of cognitive function during whole brain radiation.

See also[edit]

References[edit]

  1. ^ Reisberg B, Doody R, Stöffler A, Schmitt F, Ferris S, Möbius HJ; Memantine Study Group. (2003) Memantine in moderater-to-severe Alzheimer's disease. New Engl. J. Med. 348(14) 1333-41
  2. ^ Aarsland, D; Ballard, C; Walker, Z; Bostrom, F; Alves, G; Kossakowski, K; Leroi, I; Pozo-Rodriguez, F; Minthon, L; Londos, E (July 2009). "Memantine in patients with Parkinson's disease dementia or dementia with Lewy bodies: a double-blind, placebo-controlled, multicentre trial.". Lancet neurology 8 (7): 613–8. doi:10.1016/S1474-4422(09)70146-2. PMID 19520613. 
  3. ^ Johansson, C; Ballard, C; Hansson, O; Palmqvist, S; Minthon, L; Aarsland, D; Londos, E (February 2011). "Efficacy of memantine in PDD and DLB: an extension study including washout and open-label treatment.". International journal of geriatric psychiatry 26 (2): 206–13. doi:10.1002/gps.2516. PMID 20665553. 
  4. ^ a b Schneider, LS; Dagerman, KS, Higgins, JP, McShane, R (August 2011). "Lack of evidence for the efficacy of memantine in mild Alzheimer disease.". Archives of neurology 68 (8): 991–8. doi:10.1001/archneurol.2011.69. PMID 21482915. 
  5. ^ Mount C, Downton C (July 2006). "Alzheimer disease: progress or profit?". Nat Med. 12 (7): 780–4. doi:10.1038/nm0706-780. PMID 16829947. 
  6. ^ NICE technology appraisal January 18, 2011 Azheimer's disease - donepezil, galantamine, rivastigmine and memantine (review): final appraisal determination
  7. ^ a b Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006.
  8. ^ a b Areosa SA, Sherriff F, McShane R (2005). "Memantine for dementia". In Areosa Sastre, Almudena. Cochrane Database Syst Rev (3): CD003154. doi:10.1002/14651858.CD003154.pub4. PMID 16034889. 
  9. ^ Joint Formulary Committee (2004). British National Formulary (47th ed.). London: BMA and the Royal Pharmaceutical Society of Great Britain. ISBN 0-85369-584-9. 
  10. ^ a b Villoslada P, Arrondo G, Sepulcre J, Alegre M, Artieda J (December 2008). "Memantine induces reversible neurologic impairment in patients with MS". Neurology 72 (19): 1630–3. doi:10.1212/01.wnl.0000342388.73185.80. PMID 19092106. 
  11. ^ Green AJ (February 2009). "Understanding pseudo. The symptoms are real, the cause is unclear". Neurology 72 (19): 1626–7. doi:10.1212/01.wnl.0000345879.39454.68. PMID 19246422. 
  12. ^ a b Morris, H.; Wallach, J. (2014). "From PCP to MXE: a comprehensive review of the non-medical use of dissociative drugs". Drug Testing and Analysis. 
  13. ^ Parsons, C.; Danysz, W. (1999). "Memantine is a clinically well tolerated N-methyl-D-aspartate (NMDA) receptor antagonist—a review of preclinical data". Neuropharmacology. 
  14. ^ Bechara J. Saab, Ruxandra M. Luca, Wing B. Yuen, Adam M. P. Saab, John C. Roder "Memantine Affects Cognitive Flexibility in the Morris Water Maze", Journal of Alzheimer's Disease Volume 27 Issue 3 (December 2011).
  15. ^ Cacabelos R, Takeda M, Winblad B (January 1999). "The glutamatergic system and neurodegeneration in dementia: preventive strategies in Alzheimer's disease". Int J Geriatr Psychiatry 14 (1): 3–47. doi:10.1002/(SICI)1099-1166(199901)14:1<3::AID-GPS897>3.0.CO;2-7. PMID 10029935. 
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  17. ^ a b Chen HSV, Pellegrini JW, Aggarwal SK, Lei SZ, Warach S, Jensen FE, Lipton SA (1 November 1992). "Open-channel block of N-methyl-D-aspartate (NMDA) responses by memantine: therapeutic advantage against NMDA receptor-mediated neurotoxicity". J. Neurosci. 12 (11): 4427–36. PMID 1432103. 
  18. ^ a b Chen HSV, Lipton SA (15 February 1997). "Mechanism of memantine block of NMDA-activated channels in rat retinal ganglion cells: uncompetitive antagonism". J. Physiol. (Lond.) 499 (Pt 1): 27–46. PMC 1159335. PMID 9061638. 
  19. ^ Rogawski, MA; Wenk GL (2003). "The neuropharmacological basis for the use of memantine in the treatment of Alzheimer's disease". CNS Drug Rev 9 (3): 275–308. doi:10.1111/j.1527-3458.2003.tb00254.x. PMID 14530799. 
  20. ^ Robinson, DM; Keating GM (2006). "Memantine: a review of its use in Alzheimer's disease". Drugs 66 (11): 1515–34. doi:10.2165/00003495-200666110-00015. PMID 16906789. 
  21. ^ Xia P, Chen HSV, Zhang D, Lipton SA (2010). "Memantine preferentially blocks extrasynaptic over synaptic NMDA receptor currents in hippocampal autapses". J. Neurosci 30 (33): 11246–11250. doi:10.1523/JNEUROSCI.2488-10.2010. PMC 2932667. PMID 20720132. 
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  23. ^ Rogawski, MA (2000). "Low affinity channel blocking (uncompetitive) NMDA receptor antagonists as therapeutic agents—toward an understanding of their favorable tolerability". Amino Acids 19 (1): 133–49. doi:10.1007/s007260070042. PMID 11026482. 
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  25. ^ Lipton SA (February 2006). "Paradigm shift in neuroprotection by NMDA receptor blockade: memantine and beyond". Nature Reviews Drug Discovery 5 (2): 160–70. doi:10.1038/nrd1958. PMID 16424917. 
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  33. ^ http://www.psycheducation.org/depression/meds/memantine.htm
  34. ^ Open-Label Pilot Study of Namenda in Adult Subjects With ADHD and ADHD NOS [1]
  35. ^ Dan Ziegler. "New drugs to prevent or treat diabetic polyneuropathy" (pdf). Retrieved 2008-01-07. [dead link]
  36. ^ Schifitto G, Navia BA, Yiannoutsos CT, et al. (September 2007). "Memantine and HIV-associated cognitive impairment: a neuropsychological and proton magnetic resonance spectroscopy study". AIDS 21 (14): 1877–86. doi:10.1097/QAD.0b013e32813384e8. PMID 17721095. 
  37. ^ Corbett J (September 2007). "Memantine/Gabapentin for the treatment of congenital nystagmus". Curr Neurol Neurosci Rep 7 (5): 395–6. doi:10.1007/s11910-007-0061-z. PMID 17764629. 
  38. ^ Aman, Michael (Interviewee) (2010-07-29). Drug Used in Alzheimer's Tested In Kids With Autism. Ohio: Ohio State University Medical Center. 
  39. ^ Borghol, Amne; Kirkwood A; Hawawini F (May 2010). "Memantine for the Treatment of Migraine". US Pharm 35 (5): 28–35. 
  40. ^ Wang, R.; Zhang, D. (2005). "Memantine prolongs survival in an amyotrophic lateral sclerosis mouse model". European Journal of Neuroscience 22 (9): 2376–2380. doi:10.1111/j.1460-9568.2005.04431.x. PMID 16262676.  edit
  41. ^ Costa, ACS; Boada R; Hutaff-Lee C; Schrader A; Weitzenkamp D; Benke TA; Goldson EJ (July 17, 2012). "Antagonism of NMDA receptors as a potential treatment for Down syndrome: a pilot randomized controlled trial". Translational Psychiatry 2 (e141). doi:10.1038/tp.2012.66. 

Further reading[edit]

  • Lipton SA (2005). "The molecular basis of memantine action in Alzheimer's disease and other neurologic disorders: low-affinity, uncompetitive antagonism". Current Alzheimer research 2 (2): 155–65. doi:10.2174/1567205053585846. PMID 15974913. 

External links[edit]