N-butylscopolammonium bromide

N-butylscopolammonium bromide (also known as hyoscine butylbromide) is a potent, injectable **anticholinergic** and **antispasmodic** agent primarily used in equine medicine. * **Key Clinical Use**: Rapid relief of abdominal pain associated with spasmodic colic, flatulent colic, and simple impactions in horses. It is also used to facilitate rectal examinations and colonoscopy. * **Clinical Pearl**: Because it is a **quaternary ammonium compound**, it is highly polar and does *not* readily cross the blood-brain barrier. This means it provides excellent peripheral antispasmodic effects on the gastrointestinal and urinary tracts without the profound central nervous system (CNS) side effects (such as excitement or severe sedation) often seen with tertiary amines like atropine or scopolamine. * It has a much shorter duration of action than atropine, making it ideal for brief interventions where prolonged ileus is undesirable.

กลไกการออกฤทธิ์: N-butylscopolammonium bromide acts as a **competitive antagonist** at **muscarinic acetylcholine receptors** located on smooth muscle cells. * **Mechanism**: Blocks acetylcholine binding → prevents intracellular calcium release → induces profound relaxation of gastrointestinal and urinary smooth muscle. * **Pathway**: Parasympathetic inhibition → decreased GI peristalsis and reduced rectal pressure. * **Duration**: Visceral antinociceptive and spasmolytic effects are brief, typically lasting 15-20 minutes in horses.

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