How should sea‑sickness be prevented and treated, including drug choices, dosing, non‑pharmacologic measures, and special considerations for children, pregnancy, and contraindications?

Sea Sickness: Prevention and Treatment

First-Line Pharmacologic Prevention

Scopolamine transdermal patch is the first-line medication for preventing sea sickness and should be applied behind the ear 12 hours before anticipated motion exposure. 1, 2, 3

• The transdermal system delivers sustained medication over 72 hours and has been proven significantly more effective than placebo in controlled trials of sailors at sea 2
• For rapid-onset protection in emergency situations (e.g., survival craft evacuations), combine intramuscular scopolamine injection for immediate effect followed by transdermal patch for sustained protection 3
• Side effects are minimal at prophylactic doses, with no statistically significant adverse effects compared to placebo in clinical trials 2

Alternative Pharmacologic Options

First-generation antihistamines are effective alternatives when scopolamine is contraindicated, though they cause sedation. 1

• Meclizine is FDA-approved for motion sickness prevention and treatment 4
• Antihistamines work by blocking H1-receptors, as histamine levels increase during motion sickness episodes 2
• Important caveat: Nonsedating antihistamines, ondansetron, and ginger root are NOT effective for motion sickness prevention or treatment 1

Non-Pharmacologic Strategies

Behavioral modifications should be implemented alongside medications to maximize effectiveness. 1

• Positioning: Stay in the most stable part of the vessel (center of ship, near waterline); lie down with eyes closed if symptoms develop 1
• Visual strategies: Watch the true horizon; avoid reading or looking at screens; steer the vehicle if possible 1
• Gradual adaptation: Slow, intermittent exposure to motion reduces symptoms over 2-3 days 5, 6
• Head positioning: Tilt head into turns to align vestibular signals with visual input 1
• Minimize other physical, mental, and emotional stressors that compound susceptibility 1

Special Populations

Children

• Children aged 2-12 years are most susceptible to motion sickness 5
• Meclizine dosing must be calculated carefully by body weight per FDA labeling 4
• Scopolamine and first-generation antihistamines are the primary options 5, 1

Pregnancy

• Women are more susceptible than men, with increased risk during menstruation and pregnancy 5
• Meclizine is FDA-labeled for use in pregnancy (see specific FDA guidance) 4
• Scopolamine transdermal may be considered, though consultation with obstetrics is prudent 5

Contraindications and Warnings

• Drowsiness: All effective medications cause sedation; warn patients about operating machinery or performing safety-critical tasks 4, 1, 3
• Concurrent medical conditions: Screen for conditions that may be exacerbated by anticholinergic effects (glaucoma, urinary retention, cognitive impairment in elderly) 4
• Drug interactions: CNS depressants and CYP2D6 inhibitors potentiate sedation with meclizine 4

Clinical Pitfalls

• Timing is critical: Medications must be started BEFORE motion exposure; they are less effective once symptoms begin 1, 2
• Adaptation takes time: Most people adapt within 72 hours, so symptoms are typically self-limited 5, 6
• Overcrowding worsens outcomes: Ensure adequate ventilation, temperature control, and space to reduce anxiety and secondary factors 3
• Dehydration risk: Provide antiemetic bags, electrolytes, and potable water, especially in prolonged exposure scenarios 3
• Up to 80% of sailors experience sea sickness despite modern vessel technology, so aggressive prophylaxis is warranted for susceptible individuals 6