text: BACKGROUND: Since the introduction of the first << cholinesterase >> inhibitor (ChEI) in 1997, most clinicians and probably most patients would consider the cholinergic drugs, [[ donepezil ]], galantamine and rivastigmine, to be the first line pharmacotherapy for mild to moderate Alzheimer's disease.The drugs have slightly different pharmacological properties, but they all work by inhibiting the breakdown of acetylcholine, an important neurotransmitter associated with memory, by blocking the enzyme acetylcholinesterase.