What is the recommended use and dosage of Hyoscine (scopolamine) for motion sickness and preoperative secretion reduction?

Hyoscine (Scopolamine): Clinical Use and Dosing

Primary Indications and Dosing

Hyoscine (scopolamine) is primarily indicated for motion sickness prevention and preoperative secretion reduction, with specific dosing varying by route of administration and clinical context.

Motion Sickness Prevention

For motion sickness, transdermal scopolamine is the most effective single agent available, delivering 0.5 mg over 72 hours via a patch system. 1

• Apply the transdermal patch to the postauricular area 6-8 hours before anticipated motion exposure to achieve protective plasma concentrations (approximately 50 pg/mL) 1
• For faster protection when needed within 1 hour, combine patch application with oral scopolamine 0.3-0.6 mg 1
• The patch achieves steady-state plasma concentrations of approximately 100 pg/mL within 8-12 hours, providing optimal protection during this timeframe 1
• Replace the patch every 72 hours by applying a new one behind the opposite ear 1

Oral dosing (when transdermal unavailable): 2

• Adults and children ≥12 years: 1-2 tablets (0.3 mg each) every 4 hours as needed, maximum 12 tablets in 24 hours
• Children 2 to <12 years: 0.5-1 tablet every 4 hours as needed, maximum 6 tablets in 24 hours
• Tablets may be taken sublingually, orally, or chewed 2

Preoperative Secretion Reduction

For awake tracheal intubation and preoperative antisialagogue use: 3

• Intramuscular route: 0.2-0.6 mg administered 30-60 minutes pre-procedure 3
• Intravenous route: 5-10 minutes onset, with longer systemic effects (approximately 4 hours duration) compared to glycopyrronium or atropine 3
• Note: Hyoscine may produce tachycardia, dizziness, and sedation—effects that distinguish it from other antisialagogues 3

Palliative Care Applications

For secretion management in end-of-life care: 3

• Scopolamine 0.4 mg subcutaneously every 4 hours as needed for excessive secretions when estimated life expectancy is in weeks 3
• Consider for patients with bowel obstruction when gut function cannot be maintained, using anticholinergics to reduce secretions 3

Critical Clinical Considerations

Contraindications and High-Risk Populations

Avoid hyoscine in elderly patients when used for postoperative nausea and vomiting prophylaxis, as anticholinergics can cause cognitive impairment and increase delirium risk. 3

• The transdermal formulation should specifically be avoided in elderly patients due to these risks 3
• All anticholinergics can cause blurred vision, dry mouth, dilated pupils, urinary retention, and sedation 3
• Significant toxicity and withdrawal effects can occur with use beyond several days 3

Common Adverse Effects

Expect dry mouth in 50-60% of patients, drowsiness in up to 20%, and allergic contact dermatitis in 10% with transdermal use. 1

• Transient impairment of ocular accommodation occurs, sometimes from finger-to-eye contamination after patch handling 1
• Toxic psychosis has been reported, particularly in elderly and pediatric patients 1
• Anticholinergic syndrome can occur with unintentional overdose, presenting with CNS depression and anticholinergic symptoms 4

Pharmacokinetic Considerations

Oral scopolamine has limited bioavailability (only 2.6% excreted unchanged in urine), suggesting significant first-pass metabolism. 5

• Grapefruit juice significantly increases scopolamine bioavailability by inhibiting intestinal CYP3A, increasing AUC to approximately 142% of control values 5
• The short plasma half-life and dose-dependent adverse effects (particularly hallucinations) limit clinical use of oral and parenteral formulations 5
• Scopolamine readily crosses the placenta and should only be administered to pregnant women under close observation 5

Comparative Efficacy

Transdermal scopolamine reduces motion sickness incidence and severity by 60-80% compared to placebo (p=0.0001). 6

• Superior to oral meclizine or cinnarizine 1
• Similar efficacy to oral scopolamine 0.6 mg or promethazine plus ephedrine 1
• Produces approximately half the drowsiness incidence of oral dimenhydrinate or cinnarizine 1
• The selective M3/m5 muscarinic antagonist zamifenacin showed similar anti-motion sickness efficacy to hyoscine, suggesting these receptor subtypes mediate the therapeutic effect 7

Important Clinical Pitfalls

Do not use hyoscine or other vestibular suppressants as primary treatment for benign paroxysmal positional vertigo (BPPV)—repositioning maneuvers are the definitive treatment. 3

• Vestibular suppressants may only be offered for short-term management of severe vegetative symptoms (nausea, vomiting) during acute BPPV attacks 3
• For Ménière's disease, offer only a limited course of vestibular suppressants during acute vertigo attacks, not for chronic management 3
• All benzodiazepines carry significant drug dependence risk when used as vestibular suppressants 3

Performance impairment with prolonged use: Repeated or prolonged transdermal application may impair memory storage for new information, though short-term use does not affect performance 1