One of the forms how the disruption of normal functioning of the nervous system can be manifested is dementia. The genesis of dementia may have different natures: vascular dementia, fronto-temporal dementia, dementia in Parkinson's disease, dementia with Lewy bodies, and others. However, most frequently it is caused by Alzheimer's disease. The clinical picture of dementia during Alzheimer's disease is accompanied by predominant memory impairment and related cognitive disorders (apraxia, aphasia, agnosia, etc.) and defects.
The mechanism of dementia is determined by significant decline in the number of the cholinergic neurons. However, cholinergic dementia can occur at any age. This pathogenesis is associated with the diminished action of the acetylcholine – neurotransmitter that provides transmission of nerve impulses between synapses of nerve cells. Reduced number of neurons or slight effect of acetylcholine actions lead to the disruption of brain cells and thus to the development of cognitive impairment and defects as well as the loss of memory. Therefore, the pathogenetic treatment that provides relief of clinical symptoms rather than eliminates the cause of the disease is associated with the continuation of acetylcholine production. It is possible by blocking acetylcholine esterase – a specific enzyme responsible for the degradation and uncoupling of acetylcholine and its physiological utilization. Inhibition of this enzyme will make the action of acetylcholine more effective and prolonged and, therefore, improve the brain’s function. There are similar and different in effects drugs that provide an adequate treatment of the symptoms of this disease. An understanding of each of them will justify the choice of the active substance at different stages of the disease taking into account individual possible side effects.
Donepezil is the main active ingredient of Aricept that belongs to the group of reversible inhibitors of choline esterase. Exelon is quite a similar drug, but it provides acetylcholinesterase and butyrylcholinesterase block. Its active ingredient Rivastigmine is not selective cholinesterase inhibitor, unlike Donepezil. These drugs also differ in shape and the way of elimination from the body. Therefore, you should consider these factors when administering the drugs to patients given the possibility of individual reactions.
Unlike the previous two drugs, Namenda includes active ingredient memantine acting on glutamate system by blocking the appropriate glutamatergic receptors. However, despite the significant effectiveness and prevalence of Donepezil and Aricept in the pharmaceutical market, the drug is still used in choosing a treatment algorithm of dementia. Moreover, it is appropriate to use it in treating various forms of disease complexity.
The article by Grainger and Keegan (2011) describes a clinical case of dementia treatment option using Donepezil. After reviewing the anamnesis of the disease and a detailed clinical examination, Dougie was prescribed Aricept with dose variation depending on the duration of treatment. Also, during the study, the possible presence of cardio-vascular abnormalities was verified as this group of drug have an effect on cardiac function. During the treatment, the patient and his family noted a positive trend in cognitive activity as long as there were no seizures. The attack that happened was a side effect of Donepezil. However, due to the family point and the patient's understanding of the risk of further attacks, it was decided to continue the drug treatment, because it ensures a relatively normal life in the society. Also, Dougie agreed to take an anticonvulsant.
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In conclusion, the choice of drugs for dementia treatment is still an open question. Understanding the pharmacokinetics and pharmacodynamics of the drug will help to adequately choose the most reasonable method of treatment given the pathogenesis of the disease and the possibility of individual’s adverse reaction as significant risk factors. Therefore, a detailed history of the patient’s disease and life and a full clinical examination may determine possible choices of Aricept, Exelon or Namenda as existing medications to relieve symptoms of dementia.
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