<prompt> Constipation is caused by all of the following drugs exceptNeostigmineAtropineMorphineFentanyl  <response>: Ans. A NeostigmineRef: KDT 6the p101, 455Neostigmine is an inhibitor of acetylcholinesterase and thus acts like a cholinergic drug. Therefore, it can produce diarrhea not constipation.Atropine is an anti-cholinergic drug, thus can cause constipation.Morphine and fentanyl are opioids. These can also result in constipation. 