About donepezilcentral acetylcholinesterase inhibitor, antidementia agent in alzheimer`s disease.mechanism of action of donepezilalzheimer`s disease may result from a deficiency in neurotransmitters used by nerves in the brain to communicate with one another. donepezil exerts its therapeutic effect by enhancing its cholinergic function. it increases the concentration of acetylcholine through reversible inhibition of acetyl cholinesterase enzyme which is involved in the hydrolysis of acetylcholine. it leads to increased concentration of acetylcholine.this increased acetylcholine concentrations are believed to be responsible for the improvement seen during treatment with donepezil.interactions for donepezilantiarrhythmics: procainamide, quinidine and probably propafenone antagonise effect of neostigmine & pyridostigmine. antibacterials : aminoglycosides, clindamycin & colistin antagonise effect of neostigmine & pyridostigmine. antimuscarinics: antagonism of effect.