Hyoscine Hydrobromide

Approved Indications:

• Motion Sickness:
• Prevention and treatment of nausea, vomiting, and dizziness associated with motion sickness (air, sea, or land travel).
• Postoperative Nausea and Vomiting (PONV):
• Prophylaxis and management of nausea and vomiting following general anesthesia and surgery.
• Gastrointestinal Spasm and Irritable Bowel Syndrome (IBS):
• Relief of abdominal cramps, spasms, and colicky pain in functional GI disorders.
• Parkinsonism (adjunctive):
• Relief of sialorrhea (excessive salivation) and muscle rigidity in Parkinson’s disease.
• Palliative Care:
• Management of respiratory secretions and death rattle in end-of-life care.

Clinically Accepted Off-label Uses:

• Vestibular disorders such as Meniere’s disease and labyrinthitis (for vertigo and nausea control).
• Pre-anesthetic medication to reduce salivation and secretions.
• Acute vestibular neuritis to relieve motion-induced nausea.

Routes of Administration:

• Oral tablets
• Transdermal patch
• Subcutaneous (SC), Intramuscular (IM), Intravenous (IV) injection

Adults:

• Oral:
  300–600 micrograms (mcg) up to 3 times daily, taken 30 minutes before travel for motion sickness.
• Transdermal Patch (Scopolamine Patch):
  Delivers 1.5 mg over 72 hours. Apply behind the ear 4 hours before travel. Replace every 72 hours as needed.
• Injectable (IM/SC/IV):
  200–600 mcg every 4–6 hours as needed.
  Commonly used in palliative care for secretion management.

Pediatrics:

• Children over 10 years (Oral):
  150–300 mcg, 2–3 times daily.
  Use with caution.
• Transdermal Patch:
  Not recommended in children under 10 years due to increased risk of CNS side effects.

Elderly:

• Start at lower doses; monitor closely for confusion, hallucinations, or urinary retention.

Special Populations:

• Renal Impairment:
  Use with caution. No specific dosage adjustments, but increased risk of CNS effects.
• Hepatic Impairment:
  Use cautiously; monitor for exaggerated anticholinergic effects.

Administration Notes:

• Transdermal patch must be applied to clean, dry, hairless skin behind the ear. Avoid touching eyes after handling.
• Oral tablets should be taken with water.
• Injectables should be administered under medical supervision.

Hyoscine Hydrobromide (Scopolamine) is a tertiary amine antimuscarinic agent that acts primarily on central muscarinic (M1) receptors in the vestibular nuclei and vomiting center of the brainstem. It blocks the transmission of cholinergic signals from the vestibular apparatus to the nucleus tractus solitarius and chemoreceptor trigger zone, thus preventing motion-induced nausea and vomiting. Unlike hyoscine butylbromide, it crosses the blood-brain barrier, allowing it to exert significant central nervous system effects, including sedation and antiemesis.

• Absorption:
• Rapid and well-absorbed orally and transdermally.
• Peak plasma levels occur:
• Oral: within 1 hour
• Transdermal patch: 6–8 hours after application
• Distribution:
• Widely distributed throughout the body.
• Crosses the blood-brain barrier and placenta.
• Present in breast milk.
• Metabolism:
• Extensively metabolized in the liver via hydrolysis and conjugation.
• Elimination:
• Excreted primarily in urine as metabolites.
• Minor excretion in feces.
• Half-life:
• Oral: ~4.5 hours
• Transdermal: sustained release over 72 hours
• Bioavailability:
• Moderate (oral); higher via transdermal and parenteral routes.

• Pregnancy:
• FDA Category C
• Animal studies suggest potential fetal risk; no adequate human data.
• May be used during pregnancy if clearly needed, especially for severe motion sickness or PONV.
• Lactation:
• Excreted in breast milk.
• May cause sedation or feeding difficulty in the infant.
• Not recommended unless benefits outweigh risks.
• Caution:
• Avoid prolonged or high-dose use during pregnancy or lactation.
• Transdermal patches are generally avoided in nursing mothers.

• Primary Class: Antiemetic
• Subclass: Central Anticholinergic (Muscarinic Receptor Antagonist)
• Chemical Class: Tertiary Amine Alkaloid (Belladonna derivative)

• Hypersensitivity to hyoscine, scopolamine, or any belladonna alkaloids
• Angle-closure glaucoma
• Prostatic hypertrophy with urinary retention
• Myasthenia gravis
• Gastrointestinal obstruction or paralytic ileus
• Severe ulcerative colitis or toxic megacolon
• Use in children under 10 years (transdermal form)

• Use caution in:
• Elderly patients (higher risk of confusion, delirium)
• Individuals with cardiovascular disease, especially tachyarrhythmias
• Patients with hepatic or renal impairment
• CNS Effects:
• May cause drowsiness, hallucinations, confusion, especially in older adults.
• Visual disturbances (blurred vision, photophobia) may impair driving or operating machinery.
• Transdermal form may cause local skin reactions or delayed CNS effects.
• Overdose symptoms include:
• Dry mouth, flushed skin, agitation, tachycardia, seizures, respiratory depression.

Common Side Effects:

• Neurological:
• Drowsiness, dizziness, confusion
• Headache, restlessness
• Ocular:
• Blurred vision, photophobia, dilated pupils
• Gastrointestinal:
• Dry mouth, constipation, nausea
• Dermatologic (transdermal use):
• Skin irritation at patch site

Serious or Rare Side Effects:

• Hallucinations, disorientation, agitation
• Tachycardia or palpitations
• Urinary retention
• Angle-closure glaucoma
• Anaphylaxis (very rare)

Timing & Severity:

• CNS effects typically occur within 30–60 minutes of oral or parenteral use.
• Transdermal effects may emerge slowly and persist for days.
• Dose-dependent severity; more pronounced with systemic absorption.

Major Drug-Drug Interactions:

• Other anticholinergics (e.g., atropine, diphenhydramine): Increased anticholinergic burden
• CNS depressants (e.g., benzodiazepines, alcohol, opioids): Enhanced sedation and cognitive impairment
• Tricyclic antidepressants (TCAs) and MAOIs: Potentiation of CNS and anticholinergic side effects
• Antipsychotics: Increased risk of confusion and delirium

Drug-Food Interaction:

• No significant interaction, though food may delay onset of oral absorption slightly.

Drug-Alcohol Interaction:

• Avoid alcohol—increased risk of sedation and impaired coordination.

Enzyme Systems:

• Not a major CYP450 substrate; hepatic metabolism via non-CYP enzymatic pathways.

• FDA and EMA continue to support transdermal scopolamine patch use for PONV and motion sickness in adults.
• MHRA (UK) updated labeling to include clear guidance on use in palliative care for respiratory secretion control.
• Clinical guidelines highlight delirium risk in elderly, leading to cautionary use or avoidance in dementia patients.
• New recommendations emphasize glove use when handling transdermal patches to avoid inadvertent exposure.

Tablets:

• Store at 20°C to 25°C
• Protect from moisture and light
• Keep in tightly closed containers

Transdermal Patch:

• Store below 25°C
• Do not freeze
• Store in original pouch until use
• Discard used patch safely to prevent accidental exposure

Injectable Form:

• Store at 2°C to 8°C (refrigerated)
• Do not freeze
• Protect from light
• Use clear, particle-free solutions only