About Hyoscine Butyl Bromide Anti-cholinergic, a tropane alkaloid, Antispasmodic in GI and GU spasm. Mechanism of Action of Hyoscine Butyl Bromide Hyoscine butyl bromide is an anticholinergic drug. It exerts its action by inhibiting muscarinic (cholinergic) receptors on smooth muscles and prevents the effect of Acetylcholine. Inhibition of Acetylcholine produces relaxation of smooth muscles of gastrointestinal tract and genitourinary tract and reduces the painful spasm and cramp. It does not produce CNS effect. Antivertigo: Hyoscine suppresses the end organ receptors or inhibit central cholinergic pathway in vestibular nuclei. General anaesthesia: Once muscle paralysis is no longer desired, acetyl cholinesterase inhibitors are combined with a muscarinic receptor antagonist such as Glycopyrrolate or Hyoscine or Atropine to offset the muscarinic activation resulting from esterase inhibition