Can Allegra (fexofenadine) be used as an antihistamine for motion sickness?

Allegra (Fexofenadine) Is Not Effective for Motion Sickness

Allegra (fexofenadine) should not be used for motion sickness as it has been shown to be ineffective for this purpose. 1

Why Fexofenadine Is Not Recommended for Motion Sickness

• Fexofenadine is a second-generation antihistamine with selective peripheral H1-receptor antagonist activity that does not cross the blood-brain barrier 2
• Studies have specifically demonstrated that fexofenadine fails to prevent motion sickness in controlled trials 1
• Nonsedating antihistamines (like fexofenadine) are not effective in the prevention and treatment of motion sickness 3

Antihistamines and Motion Sickness - What Works and Why

• First-generation antihistamines (such as dimenhydrinate and meclizine) are effective for motion sickness because they:

  • Cross the blood-brain barrier and affect central nervous system function 4
  • Have suppressive effects on the central emetic center to relieve nausea and vomiting associated with motion sickness 5
  • Are considered first-line medications for motion sickness prevention 3

• The sedative properties of first-generation antihistamines appear to be crucial for their effectiveness against motion sickness 1

Pharmacological Differences Between Antihistamine Classes

• Second-generation antihistamines like fexofenadine:

  • Do not cross the blood-brain barrier 2
  • Have minimal to no sedative effects at recommended doses 5
  • Lack the central nervous system effects needed to prevent motion sickness 1

• First-generation antihistamines:

  • Readily cross the blood-brain barrier 4
  • Cause sedation and performance impairment 5
  • Are effective for motion sickness but have significant side effects 3

Recommended Alternatives for Motion Sickness

• Scopolamine (transdermal) is considered a first-line medication for prevention of motion sickness 3
• First-generation antihistamines that are effective for motion sickness include:
  • Dimenhydrinate 6
  • Meclizine 7
  • Diphenhydramine 5

Important Cautions When Using Antihistamines for Motion Sickness

• First-generation antihistamines can cause:

  • Sedation and drowsiness (66% vs 44% with placebo) 6
  • Performance impairment that may occur without subjective awareness 5
  • Increased risk of accidents when driving or operating machinery 5
  • Anticholinergic effects (dry mouth, constipation, urinary retention) 5

• Particular caution should be used in:

  • Older adults who are more sensitive to adverse effects 5
  • Patients with glaucoma, prostatic hypertrophy, or cognitive impairment 5
  • Those taking other CNS depressants, including alcohol 5

Clinical Decision Algorithm for Motion Sickness Management

1. For motion sickness prevention:

   • First choice: Scopolamine patch (apply several hours before travel) 3
   • Alternative: First-generation antihistamines (meclizine, dimenhydrinate) 6
   • Not recommended: Second-generation antihistamines like fexofenadine (Allegra) 1

2. For patients concerned about sedation:

   • Use behavioral strategies (watching the horizon, positioning in stable part of vehicle) 3
   • Consider lower doses of first-generation antihistamines 5
   • Do not substitute second-generation antihistamines as they are ineffective 1