SCOPOLAMINE
Clinical safety rating: safe
Animal studies have demonstrated safety
Scopolamine is a competitive antagonist of muscarinic acetylcholine receptors (M1, M2, M3, M4, M5), blocking the action of acetylcholine at these receptors in the central nervous system and periphery.
| Metabolism | Hepatic metabolism primarily via CYP3A4 isoenzyme, with minor contribution from other CYP450 enzymes. |
| Excretion | Renal excretion of unchanged drug and metabolites accounts for approximately 50% of elimination; biliary/fecal excretion accounts for the remainder. |
| Half-life | Terminal elimination half-life is approximately 2–4 hours in adults; in elderly or hepatic impairment, half-life may be prolonged. |
| Protein binding | Approximately 45% bound to albumin. |
| Volume of Distribution | Approximately 1–2 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: approximately 25–30% due to first-pass metabolism; transdermal: approximately 20–30%. |
| Onset of Action | IM/SC: 0.5–1 hour; IV: within minutes; oral: 1–2 hours; transdermal: 4–6 hours. |
| Duration of Action | IM/SC: 4–6 hours; IV: 2–4 hours; oral: 4–6 hours; transdermal: up to 72 hours. |
1.5 mg transdermal patch applied to postauricular skin every 72 hours; for prevention of motion sickness, apply 4-5 hours before exposure. Alternatively, 0.3-0.65 mg intramuscularly or intravenously every 6-8 hours as needed; or 0.4-0.8 mg subcutaneously. Oral dose: 0.4-0.8 mg every 6-8 hours as needed.
| Dosage form | SYSTEM |
| Renal impairment | For transdermal or oral use: no adjustment required. For parenteral administration: in severe renal impairment (GFR <10 mL/min), reduce dose by 50% or extend interval. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: consider dose reduction by 50% due to decreased clearance. Child-Pugh C: avoid use or use with caution with 75% dose reduction. |
| Pediatric use | Weight-based: 0.006 mg/kg intramuscularly or intravenously every 6-8 hours; maximum single dose 0.3 mg. Oral: 0.006 mg/kg every 6-8 hours; maximum 0.3 mg/dose. Transdermal: not recommended in children <12 years. For motion sickness prophylaxis: 0.3 mg orally 1 hour before travel, then 0.3 mg every 6-8 hours if needed. |
| Geriatric use | Lower initial doses recommended: transdermal patch 1.5 mg every 72 hours, but increase interval to 96 hours if side effects occur. Parenteral: 0.2-0.3 mg every 6-8 hours. Avoid in patients with significant cognitive impairment or increased susceptibility to anticholinergic side effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other anticholinergic drugs can have additive effects Can cause drowsiness and confusion.
| Breastfeeding | Not recommended due to potential anticholinergic effects in infant (e.g., tachycardia, constipation). Excretion in breast milk minimal; no M/P ratio available. Use with caution only if essential. |
| Teratogenic Risk | No documented teratogenicity in animal studies; limited human data. FDA Pregnancy Category C. Use only if benefit outweighs risk, especially during first trimester. Crosses placenta; potential for fetal tachycardia and reduced variability on heart rate monitoring if used near term. |
■ FDA Black Box Warning
Transdermal scopolamine may cause severe allergic reactions including anaphylaxis and angioedema. Additionally, use in patients with glaucoma may lead to increased intraocular pressure.
| Common Effects | nausea |
| Serious Effects |
["Hypersensitivity to scopolamine or any component of the formulation","Narrow-angle glaucoma","Acute hemorrhage with unstable cardiovascular status","Myasthenia gravis","Pyloric obstruction, prostatic hypertrophy, or urinary retention (relative contraindications)"]
| Precautions | ["Use with caution in patients with pyloric obstruction, urinary bladder neck obstruction, or prostatic hypertrophy due to anticholinergic effects.","May precipitate acute glaucoma in patients with narrow-angle glaucoma.","Avoid use in patients with compromised cardiovascular function as it may cause tachycardia and decreased cardiac output.","Central nervous system effects such as drowsiness, disorientation, and hallucinations may occur, especially in elderly patients.","Abrupt discontinuation may cause withdrawal symptoms (dizziness, nausea, vomiting)."] |
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| Fetal Monitoring |
| Monitor maternal heart rate and blood pressure for anticholinergic effects. Fetal heart rate monitoring if used during labor; risk of fetal tachycardia and decreased beat-to-beat variability. |
| Fertility Effects | No known adverse effects on fertility. Anticholinergic effects may dry cervical mucus, possibly affecting sperm penetration; clinical significance uncertain. |