Toward an effective treatment of Alzheimer's disease
Two theoretical problems are worth noting. Although the cholinergic deficit is characteristic of Alzheimer's disease, deficits in other neurotransmitter systems also develop, particularly in the late stages of the disease, although it has been argued that these patients may not have 'pure' Alzheimer's disease. It seems likely that treatment directed at only one neurotransmitter system may not be optimal for patients with multiple neurotransmitter deficiencies. It should be remembered that the treatment of Parkinson's disease with levodopa does not prevent the development of late-stage Parkinson's disease even though it relieves the symptoms of patients with early-stage disease, often for years. Despite these caveats, the evidence that physostigmine therapy improves cognitive function in patients with Alzheimer's disease is very encouraging. Thus, physostigmine may be a model compound for treatment of the cholinergic system within the brain in these patients with the disease Lewis Thomas has termed the 'disease of the century'.