The cholinesterase inhibitors donepezil (Aricept), galan-tamine (Razadyne), and rivastigmine (Exelon) have received FDA approval for the treatment of patients with Alzheimer's disease. Tacrine (Cognex), which is associated with elevated liver transaminase levels in about 30% of patients, is rarely used. The cholinesterase inhibitors act by blocking acetylcho-linesterase breakdown of acetylcholine, believed to increase acetylcholine in affected areas of the brain. All these agents show comparable response rates, and choice is therefore individualized according to patient and caregiver needs as well as the drug's side effect profile. Pharmacologic effectiveness is measured by a slowing of the decline in cognitive and global functioning over 6 to 12 months. The cholinesterase inhibitors are generally well tolerated, although side effects include nausea, vomiting, diarrhea, dyspepsia, anorexia, weight loss, bradycardia, and agitation. When these medicines are discontinued, the patient may experience a rapid decline in global functioning.
Another medication, memantine (Namenda), an N-methyl-D-aspartate (NMDA) receptor antagonist, has been FDA approved for the treatment of moderate to severe dementia as monotherapy or in combination with a cholinesterase inhibitor (Reisberg, 2003). Memantine appears to have fewer side effects than the cholinesterase inhibitors, although dizziness, insomnia, and hallucination may be seen. Alternative agents such as Ginkgo biloba, nicotine, vitamin C, and vitamin E could be beneficial in the treatment of Alzheimer's disease. At present, however, no other prescribed medication, supplement, or herbal preparation can be recommended for the cognitive or functional manifestations of dementia (Hogan et al., 2008).
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