Scopolamine: Effect Against Motion Sickness

Scopolamine (Hyoscine), a tropane alkaloid from plants of the nightshade family such as henbane and datura, is a potent antagonist of muscarinic acetylcholine receptors. In Germany, two salt forms are used: tertiary scopolamine (in transdermal patches such as Scopoderm) and quaternary N-butylscopolamine (Buscopan, a separate substance with predominantly peripheral action). Because of their different pharmacology, it is important not to confuse them.

Scopolamine in patch form is the established therapy for motion sickness (kinetosis) and is also used in postoperative nausea as well as in palliative medicine for secretion control in noisy breathing at end of life. The active substance has a demanding safety profile with central anticholinergic effects, which in elderly people and with pre-existing conditions such as narrow angle glaucoma or benign prostatic hyperplasia requires careful evaluation.

Mechanism of Action

Scopolamine competitively blocks muscarinic acetylcholine receptors (M1 to M5), thereby exerting parasympatholytic effects. Unlike atropine, the tertiary form crosses the blood-brain barrier and acts centrally. In the vestibular nucleus and area postrema, scopolamine suppresses processing of contradictory sensory impressions that underlie motion sickness and reduces triggering of nausea via the vomiting center.

Peripherally, scopolamine inhibits secretion of saliva and sweat, reduces gastrointestinal motility, and leads to pupil dilation with accommodation disorders. On smooth muscle of the gastrointestinal and urogenital tract, it exerts an antispasmodic effect. These effects explain both the benefit in palliative secretion control and typical side effects such as dry mouth and visual disturbances.

Through the transdermal system, scopolamine is released slowly over up to 72 hours. The effect begins approximately four hours after application, which requires advance application before travel begins. Metabolism occurs primarily via the liver, with minor renal elimination complementing the excretion pattern.

Indications

• Motion sickness during ship, flight, bus, or car travel, especially with prolonged exposure
• Postoperative nausea and vomiting, patch applied before surgery as part of multimodal antiemesis
• Palliative secretion control for noisy breathing at end of life, often given as subcutaneous butylscopolamine or scopolamine patch
• Premedication in anesthesia, classically for secretion reduction and sedation, less commonly used today
• Hypersalivation in neurological diseases such as Parkinson syndromes or amyotrophic lateral sclerosis, individual indication

Scopolamine is not indicated for nausea resulting from chemotherapy, where 5-HT3 antagonists such as ondansetron or granisetron are the treatment of choice. For pregnancy-related vomiting, other antiemetics are preferred.

Dosage and Administration

Motion sickness patch: Apply one patch (1.5 mg scopolamine) five to eight hours before travel begins, behind the ear on dry, hairless skin. Duration of action up to 72 hours. For longer journeys, apply new patch on the other side.

Postoperative nausea: Patch one to two hours before surgery begins. Application ideally as part of a multimodal approach with dexamethasone and a 5-HT3 antagonist.

Palliative secretion control: Butylscopolamine 20 to 60 mg subcutaneously or continuously per day, in specialized settings also tertiary scopolamine. Goal is reduction of disturbing breath sounds, not complete dryness.

Wash hands after application: Residue on fingers can cause mydriasis and visual disturbances upon eye contact.

Renal insufficiency and liver insufficiency: Use cautiously in case of impaired function, lower number of patches in subsequent periods.

Elderly patients: Caution due to pronounced central anticholinergic effects. In cases of cognitive vulnerability, patches are often not the best option, alternative antiemetics or careful indication setting are preferable.

Side Effects

Very common: Dry mouth, drowsiness, visual disturbances with blurred vision.

Common: Dizziness, skin irritation at application site, dilated pupils with light sensitivity, constipation, urinary retention.

Occasional to rare: Confusion, hallucinations, memory disorders, agitation, tachycardia, accommodation disorder with double vision, allergic reactions.

With overdose or in very sensitive individuals: Anticholinergic syndrome with confusion, hallucinations, dilated pupils, tachycardia, hyperthermia, skin flushing. Antidote is physostigmine in emergency medicine.

Narrow angle glaucoma: Acute glaucoma attack possible due to pupil dilation, contraindication in manifest narrow angle glaucoma.

When changing patches: Rebound phenomena such as dizziness, nausea, or sweating may occur within 24 hours of removal, especially after prolonged use.

Drug Interactions

• Other anticholinergic agents such as tricyclics, first-generation antihistamines, phenothiazines, spasmolytic agents: additive anticholinergic effects with confusion, tachycardia, and urinary retention.
• Sedatives and CNS depressants (benzodiazepines, Z-drugs, opioids, alcohol): enhanced drowsiness, falls possible.
• Domperidone and metoclopramide: Opposing effects in gastrointestinal tract, clinical significance minimal.
• Inhaled anticholinergic agents (tiotropium, glycopyrronium, aclidinium): additional anticholinergic burden, especially with systemic absorption.
• Cholinesterase inhibitors (donepezil, rivastigmine, pyridostigmine): pharmacological antagonism, mutual reduction of effects.
• L-dopa: In Parkinson's disease, scopolamine may alter effect, rarely clinically relevant in practice.

Special Notes

Pregnancy: Only with strict indication, safer are non-anticholinergic antiemetics. If a patch is used, keep it as brief and in the lowest dose possible. Breastfeeding: Passage into breast milk, breastfeeding with ongoing patch therapy not recommended.

Children and adolescents: Scopolamine patches in Germany are generally used from 10 years of age. In younger children, confusion and paradoxical reactions are possible.

Elderly patients: Pronounced risk for confusion, falls, and urinary retention. In case of pre-existing cognitive disease, restrictive indication. Geriatric lists such as Priscus critically assess anticholinergic substances.

Pre-existing conditions: Contraindicated in manifest narrow angle glaucoma, gastrointestinal stenosis, paralytic ileus, severe benign prostatic hyperplasia with residual urine, myasthenia gravis.

Driving ability: Generally impaired, especially in the first hours and the following day. No operation of heavy machinery during entire period of use.

MRI: Some patches contain metallic components, remove before MRI.

Use in children and dogs: No direct skin contact with used patches, as residual amounts are sufficient to cause poisoning. Fold patches after use and dispose safely.

You Might Also Be Interested In

• Dimenhydrinate, first-generation antihistamine for motion sickness
• Cinnarizine, calcium antagonist and antihistamine for dizziness
• Granisetron, 5-HT3 antagonist for nausea and vomiting
• Ondansetron, another 5-HT3 antagonist for nausea
• Acetylcholine, neurotransmitter and target of anticholinergic drugs

Frequently Asked Questions

Sources

• Gelbe Liste, Scopolamine Active Substance Profile
• BfArM, Federal Institute for Drugs and Medical Devices
• AWMF, Guidelines on Travel Medicine and Palliative Medicine
• Priscus 2.0 List, Potentially Inappropriate Medication in Older Adults