Succeeding in the Marketplace

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A better drug for Alzheimer's?

FDA-approved treatments for Alzheimer’s disease

The FDA-approved drugs for AD consist of tacrine (Cognex, produced by Parke-Davis, now part of Pfizer) (6, 7), donepezil (Aricept, Esai Co.) (8), and rivastigmine (Exelon, Novartis Pharmaceuticals) (9). Although all three are designed to ameliorate the disorder by inhibiting ACh destruction, their chemical structures differ significantly, underscoring their different clinical profiles.

tacrineThe first agent to be approved was tacrine, in 1993, and it has demonstrated modest efficacy in the treatment of AD dementia. However, because of adverse side effects such as hepatotoxicity, gastrointestinal disturbances, and emesis, only a minority of patients in good health are likely to benefit from the drug, and indeed it has minimal market share at this time.

DonepezilDonepezil, approved in 1996, has rapidly gained clinical acceptance; it is better tolerated and seems to benefit the majority of mildly afflicted AD patients. Of particular significance are the effects that this drug has in stabilizing the progression of cognitive deficits associated with AD.

RivastigmineRivastigmine received FDA approval earlier this year, although it has been available in Europe since 1997. Unlike the previously approved drugs, rivastigmine is classified as an intermediate-acting agent because of its long-lasting inhibition of cholin esterase (up to 10 h), despite an elimination half-life of <2 h. Initial reports of mild side effects and good patient response in the United States are encouraging.

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