What are the side effects of the scopolamine (antiemetic) patch?

Side Effects of the Scopolamine Patch

The scopolamine transdermal patch commonly causes anticholinergic side effects including blurred vision, dry mouth, drowsiness, confusion, and urinary retention, with more serious adverse effects including delirium and acute psychosis in susceptible individuals. 1

Common Side Effects

The FDA-approved drug label for scopolamine transdermal patches lists the following common side effects:

• Dry mouth (occurs in approximately 50-60% of users)
• Drowsiness or feeling sleepy (up to 20% of users)
• Blurred vision and eye problems
• Dizziness
• Confusion or disorientation
• Agitation or irritability
• Pharyngitis (sore throat)
• Dilated pupils 1, 2

Serious Side Effects

Several serious side effects require immediate medical attention:

• Angle closure glaucoma - symptoms include eye pain, blurred vision, seeing halos around lights, and eye redness
• Acute psychosis - characterized by:
  • Confusion
  • Agitation
  • Rambling speech
  • Hallucinations
  • Paranoid behaviors and delusions 1
• Worsening of seizures in patients with seizure disorders
• Difficulty urinating and urinary retention
• Gastrointestinal problems - difficulties in food passing from stomach to small intestines, causing abdominal pain, nausea or vomiting 1

Special Considerations

Withdrawal Syndrome

A unique withdrawal syndrome can occur 24-36 hours after removing the patch, especially after prolonged use. Symptoms include:

• Dizziness
• Nausea
• Sweating
• Fatigue
• Muscle weakness
• Low heart rate
• Low blood pressure
• Stomach cramps 1, 3

Central Nervous System Effects

Scopolamine crosses the blood-brain barrier and can cause significant central effects:

• Impaired memory for new information
• Reduced attention
• Decreased alertness
• Cognitive impairment 4

Anticholinergic Toxicity

In cases of toxicity or overdose, patients may present with an atypical anticholinergic syndrome:

• Altered mental status
• Visual hallucinations
• Mydriasis (dilated pupils)
• Hyperreflexia
• Dystonic movements
• Urinary retention 5

Precautions and Contraindications

The scopolamine patch should be used with caution in:

• Elderly patients (increased risk of confusion and delirium)
• Patients with glaucoma
• Patients with urinary retention or prostatic hypertrophy
• Patients with seizure disorders
• Pregnant women (crosses the placenta) 1, 6

Practical Considerations

• The onset of benefit for transdermal scopolamine patches is about 12 hours, making them inappropriate for imminently dying patients requiring secretion control 7
• Scopolamine can be administered subcutaneously if more immediate effect is needed 7
• The patch is designed to deliver approximately 1 mg of scopolamine over 3 days 1
• Limit contact with water while swimming and bathing as the patch may fall off 1
• Avoid alcohol while using the scopolamine patch as it can increase the risk of side effects 1
• Do not drive or operate heavy machinery until you know how the patch affects you 1

In palliative care settings, scopolamine is often used to reduce excessive secretions associated with dyspnea, but its side effect profile and potential for significant toxicity must be carefully considered, especially when used for more than several days 7.