Constipation is caused by all of the following drugs except: (A) Neostigmine, (B) Atropine, (C) Morphine, (D) Fentanyl
Answer is A. Ans. (A) Neostigmine(Ref: KDT 6th/e p101, 455)Neostigmine 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.