<prompt> 55yr old man with dementia was given a natural alkaloid which of the following?TacrineDonepezilGalantamineRivastigmine  <response>: Ans. is c i.e., Galantamine Galantamine: It is a natural alkaloid which selectively inhibits cereral acetylcholinesterase and has some direct agonistic action on nicotinic receptors as well. It has produced cognitive and behavioural benefits in alzheimers disease. 