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Injection Buscopan (Hyoscine Butylbromide) — Detailed Overview

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1. Basic Identity

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2. Mechanism of Action

1. Muscarinic receptor blockade — Blocks M1–M5 muscarinic acetylcholine receptors on smooth muscle cells of the GI, biliary, and genitourinary tracts → prevents acetylcholine-mediated smooth muscle contraction → spasmolysis.
2. Ganglionic blockade (nicotinic) — Also binds nicotinic receptors at parasympathetic ganglia in the visceral walls, amplifying its antispasmodic effect.

Critical distinction from scopolamine/hyoscine hydrobromide: The butyl-bromide group makes it a quaternary ammonium compound — permanently charged across the entire pH range. This prevents it from crossing the blood-brain barrier (BBB), so central anticholinergic effects (sedation, confusion, delirium) are essentially absent. This makes it the preferred antispasmodic in elderly patients where cognitive side effects must be avoided.

• Maudsley Prescribing Guidelines, 15ed — "Hyoscine butylbromide is not thought to enter the CNS, so central anticholinergic adverse effects are rare."

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3. Indications

Injectable form specifically:

• Acute GI spasm — gastric, intestinal, and colonic colic
• Renal colic — smooth muscle spasm in the ureter
• Biliary colic — spasm of the common bile duct and gallbladder
• Genitourinary spasm — bladder spasm
• Endoscopy adjunct — IV Buscopan is used to abolish duodenal motility during upper GI endoscopy and during CT colonography/MRI, improving visualisation of the duodenum (2nd and 3rd parts), bowel wall detail, and reducing motion artefact in radiology
• End-of-life / Palliative care — reduces death rattle (excessive respiratory secretions) in dying patients (equivalent efficacy to atropine and scopolamine in this setting)
• IBS — as part of antispasmodic regimen

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4. Pharmacokinetics

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5. Dose & Administration

• Can be repeated if required
• No dilution needed for the ampoule
• IV is preferred for fastest onset in acute colic

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6. Adverse Effects

Common (anticholinergic — peripheral):

• Dry mouth (xerostomia)
• Tachycardia ← most clinically important with injection
• Urinary retention
• Visual accommodation disturbances, mydriasis
• Increased intraocular pressure
• Decreased sweating / heat sensation (hypohidrosis)
• Constipation

Uncommon/Rare:

• Dizziness, flushing
• Skin reactions (urticaria, rash, erythema, pruritus, angioedema)
• Fixed drug eruptions
• Anaphylaxis / anaphylactic shock (rare but potentially fatal — monitor for 30 min after injection)
• Hypotension (especially with rapid IV injection)

Cardiac warning: Parenteral Buscopan can cause serious tachycardia and hypotension. More severe in patients with coronary artery disease, cardiac arrhythmias, hypertension, or mitral stenosis. Emergency resuscitation equipment must be available when giving IV.

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7. Contraindications

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8. Drug Interactions

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9. Special Populations

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10. Overdose Management

• Features: Exaggerated anticholinergic signs — tachycardia, urinary retention, hot dry skin, mydriasis, delirium (rare, since poor CNS penetration)
• Antidote: Physostigmine (a reversible cholinesterase inhibitor that crosses the BBB) can be used to reverse severe anticholinergic toxidrome
• Supportive care: catheterisation for urinary retention, cooling for hyperthermia

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11. Key Clinical Pearls

• Not to be confused with Hyoscine Hydrobromide (Kwells/Joy-rides for motion sickness) — that agent crosses the BBB and causes sedation/amnesia
• For renal/biliary colic, IV Buscopan is often combined with an analgesic (e.g., diclofenac or morphine) for faster and more complete pain relief
• During CT colonography and MRI enterography, IV Buscopan 20 mg reduces bowel peristalsis and improves image quality
• In palliative care, SC infusion via syringe driver is commonly used for secretion control — equally effective as atropine and scopolamine
• No significant CNS effects = safe to use in elderly, post-operative, and neurologically vulnerable patients

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