I. Dale Carroll

Occurrence

Motion sickness is the result of a conflict between the various senses in regard to motion. The semicircular canals and otoliths in the inner ear sense angular and vertical motion, while the eyes and the proprioceptors determine the body’s position in space. When signals received by the eyes or the proprioceptors do not match those being transmitted by the inner ear, motion sickness occurs. It can occur in either the presence or absence of actual motion, such as when viewing a slide through a microscope. Symptoms include nausea, vomiting, pallor, sweating, and often a sense of impending doom. Motion sickness is likely to occur when there is movement simultaneously in multiple planes, such as on amusement rides, on board ships, or during air travel.

Risk for Travelers

• All individuals, given sufficient stimulus, will develop motion sickness.
• Children 2–12 years of age are especially susceptible, while infants and toddlers seem relatively immune.
• Women, especially when pregnant, menstruating, or on hormones, are more likely to have motion sickness.
• Persons with migraine are more prone to either migraine or motion sickness at the same time as the other malady.
• Those who expect to be sick are more apt to experience symptoms.

Treatment

There are both nonpharmacologic and pharmacologic interventions for the prevention or management of motion sickness. None are ideal, and the medications typically cause drowsiness or similar adverse effects. Some feel that permitting continued exposure to motions that induce motion sickness will decondition the response and diminish the symptoms; however, most persons traveling for a limited time will understandably not be willing to endure the symptoms in the hope of deconditioning and will instead want to avail themselves of some of the suggestions that follow or the medications listed in Table 2-26.

Medications

• Antihistamines are the most commonly used and available medications, although nonsedating ones appear to be the least effective.
• Pyridoxine hydrochloride (vitamin B₆) plus doxylamine succinate (an antihistamine) is prescribed under the brand name of Diclectin in Canada and often recommended in their separate forms by clinicians in the United States.
• Sedation is the primary side effect of all the efficacious drugs.
  • Sedation is problematic when treating patients who perform essential tasks such as flying a plane or acting as crew on a ship, or in travelers who wish to participate in activities such as scuba diving or hang gliding.
• Some common prescription medications used by travelers may aggravate the nausea of motion sickness (see Table 2-27).

Medications in Children

• For symptomatic treatment of children 2–12 years of age, dimenhydrinate, 1–1.5 mg/kg per dose, or diphenhydramine, 0.5–1 mg/kg per dose up to 25 mg, can be given 1 hour before travel and every 6 hours during the trip.
• Because some children have paradoxical agitation with these medicines, a test dose should be given at home before departure.
• Scopalamine causes potentially dangerous adverse effects in children and should not be used; prochlorperazine and metoclopramide should be used with caution in children.
• Antihistamines are not FDA approved for use for the prevention or treatment of motion sickness in children. Caregivers should be reminded to always ask a physician, pharmacist, or other health-care professional if they have any questions about how to use or dose antihistamines in children before they administer the medication. Oversedation of young children with antihistamines can lead to life-threatening side effects.

Medications in Pregnancy

• Drugs with the most safety data regarding the treatment of the nausea of pregnancy would seem to be the logical first choice.
• Letter scoring of the safety of medications in pregnancy may not be helpful, and practitioners should review the actual safety data or call the patient’s obstetrical provider for suggestions.
• Web-based information may be found at www.Motherisk.org and www.Reprotox.org.

Preventive Measures for Travelers

Nonpharmacologic interventions include—

• Being aware of those situations which tend to trigger symptoms.
• Optimizing positioning—Driving a vehicle instead of riding in it, as well as sitting in the front seat of a car or bus, sitting over the wing of an aircraft or being in the central cabin on a ship can help reduce symptoms.
• Eating or drinking—Eating before the onset of symptoms may hasten gastric emptying, but in some individuals, can aggravate motion sickness. Drinking caffeinated beverages along with taking one of the medications suggested can help manage motion sickness.
• Reducing sensory input—The reduction of aggravating stimuli (e.g., lying prone, looking at the horizon, or shutting eyes) can help alleviate symptoms.
• Adding distractions—Aromatherapy using mint, lavender, or ginger (oral) helps some; flavored lozenges may help as well. They may function as placebos or, in the case of oral ginger, may hasten gastric emptying.
• Using acupressure or magnets—Advocated by some to prevent or treat nausea (not specifically for motion sickness), although scientific data are lacking.

References

1. Priesol AJ. Motion Sickness. In: Rose BD, editor. Waltham MA: UpToDate, 2008.
2. Takeda N, Morita M, Horii A, et al. Neural mechanisms of motion sickness. J Med Invest. 2001;48(1–2):44–59.
3. Benline TA, French J, Poole E. Anti-emetic drug effects on pilot performance: granisetron vs. ondansetron. Aviat Space Environ Med 1997; 68(11):998–1005.
4. FDA. Pregnancy and lactation labeling. 2008 [cited 2008 Oct 8]. Available from: www.fda.gov/cder/regulatory/pregnancy_labeling.