<prompt> Constipation is caused by all of the following drugs EXCEPT :NeostigmineAtropineMorphineFentanyl  <response>: Neostigmine is an inhibitor of acetylcholinesterase and thus acts like a cholinergic drug. Therefore, it can produce diarrhea not constipation.Atropine is an anticholinergic drug, thus can cause constipation.Morphine and fentanyl are opioids. These can also result in constipation. 