Hyoscine (scopolamine) is a competitive antagonist of muscarinic acetylcholine receptors, blocking parasympathetic nervous system activity. Its effects depend on the formulation:

1. Hyoscine Hydrobromide: Crosses the blood-brain barrier, exerting central and peripheral anticholinergic effects.
2. Hyoscine Butylbromide: Primarily acts peripherally with minimal CNS penetration.

By inhibiting acetylcholine binding, hyoscine:

• Reduces smooth muscle spasms in the gastrointestinal (GI) tract.
• Decreases salivary, bronchial, and gastric secretions.
• Suppresses vestibular input to the brain, preventing motion sickness.

Hyoscine is used for:

1. Gastrointestinal Spasms:
   • Irritable bowel syndrome (IBS), diverticulitis, and colicky pain (hyoscine butylbromide).
2. Motion Sickness:
   • Prophylaxis via transdermal patch (hyoscine hydrobromide).
3. Preoperative/Postoperative Care:
   • Reduces salivary and respiratory secretions.
4. Palliative Care:

Manages excessive respiratory tract secretions

Adults:

• Hyoscine Butylbromide (GI Spasms): 10–20 mg orally 3–4 times daily (BNF).
• Hyoscine Hydrobromide (Motion Sickness):
  • Transdermal Patch: Apply 1 patch (1 mg) behind the ear 5–6 hours before travel; replace every 72 hours.
  • Oral: 300–600 mcg 30 minutes before travel (max 1.2 mg/day).

Children:

• Motion Sickness (≥10 years): 150–300 mcg orally (BNF).
• Transdermal Patch: Not recommended for children <12 years.

Special Populations:

• Renal/Hepatic Impairment: Use with caution; reduce dose if necessary.
• Elderly: Increased sensitivity to CNS effects (e.g., confusion).

• Common: Dry mouth, blurred vision, drowsiness, constipation.
• Serious:
  • Central Effects (hydrobromide): Confusion, hallucinations, delirium.
  • Tachycardia, urinary retention, angle-closure glaucoma.
  • Skin Reactions: Itching or erythema under transdermal patch.

1. Contraindications:
   • Angle-closure glaucoma, myasthenia gravis, intestinal obstruction.
   • Severe ulcerative colitis (BNF).
2. Pregnancy/Lactation:
   • Category C: Avoid unless benefits outweigh risks.
   • Excreted in breast milk; may inhibit lactation.
3. Elderly: Higher risk of cognitive impairment; avoid prolonged use.

• Anticholinergics (e.g., tricyclic antidepressants): Additive effects (increased dry mouth, urinary retention).
• CNS Depressants (e.g., alcohol, benzodiazepines): Enhanced sedation.
• MAO Inhibitors: Potentiate anticholinergic toxicity.
• Prokinetic Agents (e.g., metoclopramide): Reduced efficacy.

• Hyoscine Hydrobromide:
  • Generic: Scopolamine.
  • Brand Names: Scopoderm® (patch), Kwells® (oral).
• Hyoscine Butylbromide:
  • Generic: Hyoscine butylbromide.
  • Brand Names: Buscopan® (oral/injection).