E. Tacrine, donepezil, rivastigmine, and galantamine

As mentioned above, patients with Alzheimer disease have a deficiency of cholinergic neurons in the CNS. This observation led to the development of anticholinesterases as possible remedies for the loss of cognitive function. Tacrine was the first to become available, but it has been replaced by others because of its hepatotoxicity. Despite the ability of donepezil, rivastigmine, and galantamine to delay the progression of Alzheimer disease, none can stop its progression. GI distress is their primary adverse effect.