There are a range of medications approved by regulatory agencies such as the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) to treat the cognitive manifestations of Alzheimer ’s disease. The drugs are mostly acetyl cholinesterase inhibitors. There is also NMDA receptor antagonist like Memantine. However no medication currently available can delay or halt the progression of the Alzheimer’s Disease..
Reduction in the activity of the cholinergic neurons is a well-known feature of Alzheimer’s disease. Acetyl cholinesterase inhibitors are employed to reduce the rate at which acetylcholine is broken down, thereby increasing the concentration of Acetyl cholinesterase in the brain and combating the loss of Acetyl cholinesterase caused by the death of cholinergic neurons. The cholinesterase inhibitors approved for the management of AD symptoms are donepezil (Aricept), Galantamine (Razadyne), and rivastigmine ( Exelon and Exelon Patch). There is evidence for the efficacy of these medications in mild to moderate Alzheimer’s disease, and some evidence for their use in the advanced stage.
Donepezil is approved for treatment of advanced AD dementia. The use of these drugs in mild cognitive impairment has not shown any effect in a delay of the onset of Alzheimer’s disease. The most common side effects are nausea and vomiting, both of which are linked to cholinergic excess. These side effects arise in approximately ten to twenty percent of users and are mild to moderate in severity.
Glutamate is a useful excitatory neurotransmitter of the nervous system, although excessive amounts in the brain can lead to cell death through a process called excitotoxicity which consists of the over stimulation of glutamate receptors. Excitotoxicity occurs not only in Alzheimer’s disease, but also in other neurological diseases such as Parkinson’s disease and multiple sclerosis. Memantine (brand names Akatinol, Axura, Ebixa/Abixa, Memox and Namenda), is a noncompetitive NMDA receptor antagonist . It acts on the glutamatergic system by blocking NMDA receptors and inhibiting their over stimulation by glutamate. Memantine has been shown to be moderately efficacious in the treatment of moderate to severe Alzheimer’s disease.
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