Scopolamine (Hyoscine)

Mechanism

Mechanism of Action

Non-selective reversible competitive antagonist of all muscarinic cholinergic receptors, with markedly superior central inhibitory potency compared to atropine. It exerts its primary therapeutic effects by blocking cholinergic transmission in the vestibular pathways that connect the inner ear to the vomiting center in the brainstem, blocking excitatory muscarinic neurotransmission induced by kinetic movement. It also has a pronounced central sedative and amnesiac effect.

Pharmacokinetics

Key Pharmacokinetics

The pharmacokinetic and tolerability profile of scopolamine largely depends on its chemical structure and specific pharmacological formulation:

Scopolamine Base (Transdermal Patch)

• Structure: Lipophilic natural tertiary amine; easily crosses the blood-brain barrier.
• Preferential indication: Prevention of vestibular motion sickness and postoperative nausea.
• Onset and duration: Place the patch at least 4 hours before the trip; constant and controlled effect for a period of up to 72 hours.

Scopolamine Butylbromide (Buscapina)

• Structure: Highly hydrophilic polar quaternary ammonium synthetic derivative; It does not cross the blood-brain barrier.
• Preferential indication: Symptomatic relief of gastrointestinal, biliary or renal colic.
• RAM profile: It lacks depressant or sedative adverse effects on the central nervous system.

Indicators and dose

Approved and Off-label Indications

Approved: Prevention of motion sickness (motion sickness) during sea or land travel; prophylaxis and control of postoperative nausea and vomiting induced by anesthesia or surgery.

Off-label: Symptomatic treatment of painful gastrointestinal or bile duct spasms; hypersecretion of saliva and respiratory secretions in terminal patients in the agonic phase.

Dosage and Adjustments

Kinetosis (Transdermal Patch): Apply a 1.5 mg patch to the hairless retroauricular area at least 4 hours before starting the trip. Change the patch every 72 hours if the trip persists. Remove after the trip and wash your hands thoroughly.

Abdominal Spasm (Butylbromide - Oral): 10 to 20 mg three to four times a day orally in adults.

Renal/hepatic adjustment: Does not require established adjustment guidelines in mild to moderate organ failure.

Security

Contraindications

Absolute: Primary narrow angle glaucoma, intestinal obstruction of mechanical etiology, myasthenia gravis.

Relative: Pyloric stenosis, urinary retention of prostatic origin, moderate renal failure, senile dementia (risk of exacerbation of the state of confusion).

Adverse Effects (ADR)

Common: Deep drowsiness, dry mouth, dry nose, mydriasis, temporary blurred vision, adynamic constipation, skin redness.

Serious: Acute atropinic psychosis, visual hallucinations, severe spatial disorientation (especially in the elderly), acute urinary retention that is difficult to resolve.

Interactions

CNS depressant agents (alcohol, opioid analgesics): Mutual potentiation of the sedative effect with incapacitating drowsiness.

Cholinolytic antiparkinsonian agents: Synergy in peripheral and central muscarinic toxicity.

Pregnancy and Breastfeeding

FDA Classification: Category C. It quickly crosses the placental barrier and can depress fetal heart rate and respiratory reactivity. It is excreted in breast milk and can decrease basal production; is discouraged.