The cholinesterase inhibitors have shown to increase cognitive function in AD. Degeneration of the basal forebrain cholinergic systems is a hallmark of AD. Acetylcholinesterase inhibitors delay the degradation of acetylcholine at the synaptic cleft, thereby enhancing cholinergic neurotransmission and reducing symptoms of AD.

The US-FDA has approved four cholinesterase inhibitors for treatment of the symptoms of AD; tacrine, donepezil, rivastigmine and galantamine.

Because of limitations involving use of tacrine (hepatotoxicity and four times daily dosing) and the availability of better tolerated cholinesterase inhibitors, tacrine will not be discussed any further in this module.