Hyoscine (Scopolamine): Clinical Use and Dosing
Motion Sickness Prevention
Hyoscine (scopolamine) is highly effective for preventing motion sickness and should be administered 6-8 hours before anticipated exposure for optimal protection. 1, 2
Dosing for Motion Sickness
Oral Administration (Hyoscine Hydrobromide):
- Adults and children ≥12 years: 1-2 tablets (0.3 mg per tablet) every 4 hours as needed, maximum 12 tablets in 24 hours 3
- Children 2 to <12 years: ½ to 1 tablet every 4 hours as needed, maximum 6 tablets in 24 hours 3
- Tablets may be taken sublingually, orally, or chewed 3
Transdermal System (TTS-S):
- Contains 1.5 mg scopolamine, delivers 0.5 mg over 72 hours at approximately 5 μg/hour 2
- Apply single patch to postauricular area at least 6-8 hours before exposure 2
- For faster protection (within 1 hour), combine patch application with oral scopolamine 0.3-0.6 mg 2
- Replace patch every 72 hours, alternating behind opposite ear 2
- Achieves protective plasma concentration (50 pg/mL) after 6 hours, steady-state (100 pg/mL) at 8-12 hours 2
Efficacy Evidence
Scopolamine demonstrates 60-80% reduction in motion sickness incidence and severity compared to placebo 2, 4. It is superior to methscopolamine and equivalent to antihistamines for prevention 4. The transdermal formulation is more effective than oral meclizine or cinnarizine, and comparable to oral scopolamine 0.6 mg or promethazine plus ephedrine 2.
Drying Secretions (Premedication)
For reducing bronchial and salivary secretions perioperatively, hyoscine is administered as a single preoperative dose. 5
The typical adult dose is 0.3-0.6 mg administered before procedures requiring secretion control 5. Pediatric dosing follows weight-based calculations similar to motion sickness protocols 3.
Important Clinical Considerations
Contraindications and Precautions
Do NOT use scopolamine for treating benign paroxysmal positional vertigo (BPPV) - vestibular suppressants like scopolamine are ineffective as primary treatment and only indicated for short-term management of severe nausea/vomiting in BPPV patients 1. These medications interfere with central compensation in peripheral vestibular conditions 1.
Adverse Effects Profile
- Dry mouth: Occurs in 50-60% of patients 2
- Drowsiness: Up to 20% (less than dimenhydrinate or cinnarizine) 2
- Allergic contact dermatitis: 10% with transdermal patches 2
- Ocular effects: Transient impairment of accommodation, mydriasis (may result from finger-to-eye contamination) 2
- CNS toxicity: Anticholinergic syndrome, toxic psychosis (particularly in elderly and pediatric patients) 5, 2
- Other: Difficulty urinating, headache, rashes 2
The transdermal system produces approximately half the drowsiness of oral dimenhydrinate or cinnarizine 2.
Critical Pitfalls to Avoid
Timing is crucial: Oral or transdermal scopolamine requires 6-8 hours for optimal effect; last-minute administration will fail 2. If immediate protection is needed, combine transdermal patch with oral dose 2.
Avoid finger-to-eye contamination after handling patches, which can cause mydriasis and cycloplegia 2. Low-dose pyridostigmine can prevent cycloplegia but not mydriasis if this occurs 2.
20-30% of patients fail to achieve protective plasma concentrations with transdermal systems, explaining some treatment failures 2. Consider oral supplementation or alternative agents if ineffective 2.
Anticholinergic syndrome risk: Unintentional overdose can cause CNS depression and full anticholinergic syndrome 5. Maximum daily limits must be strictly observed 3.
Special Populations
Performance is not affected by short-term use, but prolonged or repeated application may impair memory storage for new information 2. However, sea studies show less performance decrement compared to untreated motion sickness 2.