What are the side effects of scopolamine?

Side Effects of Scopolamine

Scopolamine can cause significant anticholinergic side effects including delirium, dry mouth, blurred vision, and urinary retention, and should be used with caution, especially in elderly and pediatric populations. 1, 2

Common Side Effects

Scopolamine, an anticholinergic medication used primarily for motion sickness prevention and management of secretions in palliative care, produces both peripheral and central nervous system effects:

Peripheral Anticholinergic Effects

• Dry mouth (occurs in 50-60% of patients) 3
• Blurred vision due to reduced visual accommodation 4, 3
• Urinary retention 2
• Reduced salivation 4
• Bradycardia 4

Central Nervous System Effects

• Drowsiness (up to 20% of patients) 3
• Delirium (more common in elderly patients) 1, 2
• Memory impairment for new information 4, 3
• Visual hallucinations 2
• Impaired attention 4
• Decreased alertness 4
• Dizziness 5

Severe or Rare Side Effects

• Anticholinergic toxicity - can present with altered mental status, mydriasis, and dystonic movements 2
• Toxic psychosis - particularly in elderly and pediatric patients 3
• Allergic contact dermatitis (approximately 10% of patients using transdermal patches) 3
• Dystonic reactions 2
• Hyperreflexia 2

Special Considerations for Different Populations

Elderly Patients

• Higher risk for central anticholinergic effects, especially delirium and toxic psychosis 3, 5
• Should generally avoid scopolamine use in this population 5

Pediatric Patients

• More susceptible to toxic psychosis 3
• Scopolamine should be avoided in pediatric populations 5

Pregnant Women

• Scopolamine readily crosses the placenta 6
• Should only be administered under careful observation 6

Pharmacokinetic Considerations

• Transdermal application (most common form):

  • Reaches protective plasma concentration (50 pg/mL) after 6 hours 3
  • Achieves steady state of approximately 100 pg/mL after 8-12 hours 3
  • Significant interindividual variations in plasma concentrations 6
  • 20-30% of subjects fail to attain protective concentrations 3

• Oral administration:

  • Limited bioavailability (only 2.6% excreted unchanged in urine) 6
  • Maximum concentration occurs approximately 0.5 hours after administration 6
  • First-pass metabolism significantly reduces effectiveness 6

Clinical Pitfalls and Management

1. Incomplete toxidrome presentation: Unlike typical anticholinergic poisoning, scopolamine toxicity may not present with all expected signs (tachycardia, dry mucous membranes, hyperpyrexia) 2

2. Hidden patches: When evaluating patients with altered mental status, thoroughly check for transdermal patches that may be hidden (e.g., behind the ear) 2

3. Treatment of toxicity: Physostigmine may be required to reverse severe anticholinergic effects, with potential need for incremental doses due to scopolamine's long duration of action 2

4. Visual effects: Visual problems may increase with repeated patch applications, with hypermetropic ("long-sighted") individuals at particular risk 4

5. Variation in response: Significant variation exists both between individuals and between different patch applications on the same individual 4

For patients requiring anticholinergic medications for secretion management in palliative care, glycopyrrolate may be a safer alternative as it does not cross the blood-brain barrier as readily and is less likely to cause delirium than scopolamine 1.