Buscopan acts as a smooth muscle antispasmodic by inhibiting the action of acetylcholine at postganglionic parasympathetic neuromuscular junctions. It does not cross the blood-brain barrier and therefore is devoid of central nervous system effects.
Buscopan is poorly absorbed from the gastrointestinal tract (< 10 per cent) and in the acute situation is normally given parenterally (intravenous, intramuscular, or subcutaneous) at a dose of 20 mg (for an adult), repeated as required. It has low plasma protein binding and is metabolized by the liver.
Side-effects are mainly those of peripheral parasympathetic blockade and, although these are less marked than with atropine, Buscopan should not be administered to patients with paralytic ileus, glaucoma, or prostatic hypertrophy.
Buscopan is commonly used to reduce smooth muscle spasm particularly during upper or lower gastrointestinal tract endoscopy. It is also used to treat the acute smooth muscle spasm of biliary and renal colic.
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