Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0012833 (dizziness)
 9,689 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cholinesterase inhibitors are currently the most established treatment strategy in Alzheimer's disease. The treatment effect appears mainly to be symptomatic. Effects on progression of the disease following long term treatment, and possible neuroprotective effects, have been investigated. Delay until nursing home placement has been reported. Three cholinesterase inhibitors, tacrine, donepezil and rivastigmine, are in clinical use. Other cholinesterase inhibitors, such as galantamine (galanthamine), metrifonate, physostigmine, eptastigmine, are currently under clinical evaluation. So far the efficacy appears to be comparable between the various cholinesterase inhibitors; treatment for up to 6 months has produced an improvement in Alzheimer's Disease Assessment Scale -- Cognitive Subscale score (ADAS-cog) of between 1.8 and 4.9 in patients with Alzheimer's disease. Tacrine, donepezil, galantamine and physostigmine are reversible inhibitors of acetylcholinesterase and butyrylcholinesterase, while metrifonate is considered to be an irreversible inhibitor and rivastigmine a pseudoirreversible inhibitor. Tacrine and physostigmine have lower bioavailability, 17 to 37% and 3 to 8%, respectively, than the other cholinesterase inhibitors such as rivastigmine, galantamine and donepezil (40 to 100%). The elimination half-life is considerably longer for donepezil (70 to 80h) in comparison to most of the other cholinesterase inhibitors (0.3 to 12h). Donepezil is therefore administered once daily in comparison to rivastigmine which is administered twice daily and tacrine which is administered 4 times daily. Simultaneous food intake lowers the plasma concentration of tacrine and reduces the adverse effects of rivastigmine. Drugs like theophylline and cimetidine have been reported to change the pharmacokinetics of tacrine and donepezil. In contrast, concomitant medication with various drugs with rivastigmine does not seem to cause any drug interactions in patients with Alzheimer's disease. Tacrine, donepezil and galantamine are metabolised via the cytochrome P450 (CYP) liver enzymes. Active metabolites are known for tacrine and galantamine. Rivastigmine is not metabolised via CYP enzymes, but via esterases and is excreted in the urine. Tacrine is associated with hepatotoxicity while other cholinesterase inhibitors seem devoid this adverse effect. Increased liver enzyme values have been observed in 49% of patients with Alzheimer's disease treated with tacrine. Rechallenge with tacrine reduces the incidence of elevated liver enzyme levels. Peripheral cholinergic adverse effects are common for the cholinesterase inhibitors, with an incidence ranging between 7 to 30%. For some cholinesterase inhibitors, such as rivastigmine, the cholinergic adverse effects such as nausea, vomiting, dizziness, diarrhoea and abdominal pain can be reduced by slowing the rate of dose titration.
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PMID:Cholinesterase inhibitors in the treatment of Alzheimer's disease: a comparison of tolerability and pharmacology. 988 90

In Alzheimer's disease, cognition now responds to several drugs. Anticholinesterases target the acetylcholine deficit. In mild-to-moderate Alzheimer's disease, they all provide significant benefit versus placebo on the Alzheimer's Disease Assessment ScheduleCognitive Section (ADAS-Cog), Side effects, in 5% to 15% of cases, include nausea, vomiting, diarrhea, anorexia, and dizziness. Tacrine, the leading anticholinesterase, caused frequent hepatic enzyme elevation and was withdrawn; once-daily donepezil spares the liver and improves global measures of change in severe dementia; rivasiigmine is indicated in comorbid vascular disease; while galaniamine modulates the cerebral nicotinic acetylcholine receptors that potentiate the response to acetylcholine. Alternative agents include the N-methyl-D-aspartate (NMDA) receptor antagonist, memaniine, licensed in Europe for moderately severe to severe Alzheimer's disease; it acts on a different neurotransmitter system present in 70% of neurons, protecting against pathologic glutamergic activation while preserving or even restoring physiologic glutamergic activation. The clinician's armamentarium in AD has never been greater.
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PMID:Treatment of cognitive impairment in Alzheimer's disease. 2203 58