What are the best medications for preventing and treating motion sickness and acute mountain sickness?

Best Medications for Motion Sickness and Acute Mountain Sickness

For motion sickness prevention and treatment, scopolamine is the first-line medication, while acetazolamide at 125 mg twice daily is the most effective medication for acute mountain sickness prevention with the best evidence and side effect profile.

Motion Sickness Management

Prevention of Motion Sickness

1. First-line pharmacological options:

   • Scopolamine (transdermal): Apply patch several hours before anticipated motion exposure 1
   • First-generation antihistamines:
     • Dimenhydrinate: FDA-approved for prevention and treatment of nausea, vomiting, or vertigo of motion sickness 2
     • Diphenhydramine
     • Promethazine (phenothiazine with antihistamine properties)

2. Ineffective medications (avoid using):

   • Non-sedating antihistamines
   • Ondansetron
   • Ginger root 1

Behavioral Strategies (to complement medication)

• Position yourself in the most stable part of the vehicle
• Watch the true visual horizon
• Steer the vehicle when possible
• Tilt head into turns
• Lie down with eyes closed if symptoms worsen
• Reduce exposure to unpleasant motion
• Minimize other sources of physical or emotional discomfort 1

Acute Mountain Sickness Management

Prevention of Acute Mountain Sickness

1. First-line pharmacological prevention:

   • Acetazolamide: 125 mg twice daily
     • Most effective dose with adequate evidence and fewer side effects 3
     • Provides 48% relative risk reduction compared to placebo 4
     • Higher doses (250 mg or 375 mg twice daily) are equally effective but have more side effects 3

2. Alternative preventive medications:

   • Dexamethasone: Effective but should be reserved for those who cannot tolerate acetazolamide 3
   • Ibuprofen: Reduces incidence of AMS but less evidence than acetazolamide 3

3. Non-pharmacological prevention:

   • Slow ascent (<400 m/day above 2,500 m) - most effective prevention 5
   • Rest day for every 600-1200 m gained 5
   • Pre-acclimatization for 2 weeks when possible 5
   • Minimize physical activity before acclimatization 5
   • Maintain proper hydration 5

Treatment of Acute Mountain Sickness

1. Mild to moderate AMS:

   • Stop ascent and rest
   • Acetazolamide 250 mg twice daily if not already taking for prevention
   • Adequate hydration
   • Analgesics for headache

2. Severe AMS or progression to high-altitude cerebral edema:

   • Immediate descent (minimum 300 m) - primary treatment 5, 6
   • Supplemental oxygen to maintain SpO₂ >90% 5
   • Dexamethasone for cerebral symptoms 5
   • Nifedipine if descent is impossible or delayed 5
   • Portable hyperbaric chamber if descent not possible 6

Special Considerations

Sex Differences

• Women may have higher vulnerability to acute mountain sickness 7
• For women, mid-luteal phase may be more appropriate for acute exposure to high altitude 5
• Sex hormones influence hypoxia responses 7

Cardiovascular Patients

• Patients should continue pre-existing medications at high altitude 7
• Wait at least 6 months after uncomplicated acute coronary syndrome or revascularization before high altitude exposure 7
• Acetazolamide may reduce risk of subendocardial ischemia at high altitude 7

Common Pitfalls to Avoid

• Do not use vestibular suppressant medications (antihistamines or benzodiazepines) as primary treatment for vertigo conditions like BPPV 7
• Do not rely on non-sedating antihistamines, ondansetron, or ginger for motion sickness 1
• Do not ascend too quickly (>400 m/day above 2,500 m) 5
• Do not ignore early symptoms of AMS - early recognition and treatment prevents progression to more severe forms 6

By following these evidence-based recommendations, most individuals can effectively prevent and manage both motion sickness and acute mountain sickness, reducing morbidity and improving quality of life during travel.