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Carsickness
Motion Sickness

Motion sickness, a common problem in travelers by automobile, train, air, and particularly sea, usually causes mild to moderate discomfort but in severe cases can be incapacitating. It affects up to 58% of children traveling in automobiles or airplanes and almost 100% of boat passengers in very rough seas. Motion sickness is more common in women, especially during pregnancy or menstruation, but in general little is known about individual susceptibility. Sensation of head position and movement are generated in the semicircular canals (angular acceleration or rotation) and otolith organs (vertical acceleration) in the inner ears and carried to the central nervous system via cranial nerve VIII. The signs and symptoms of motion sickness occur when sensory information about the body's position in or movement through space is contradictory or contrary to prior experience. Resulting signs and symptoms include dizziness, nausea, vomiting, pallor, and cold sweats.

Travelers who are susceptible to motion sickness can minimize symptoms by choosing seats with the smoothest ride (front seat of a car, forward cars of a train, and the seats over the wings in an airplane), focusing on distant objects rather than trying to read or look at something inside the vehicle, minimizing head movement, and if necessary lying supine.

Medications which may ameliorate symptoms of motion sickness include scopolamine (available in both patch and oral form) and oral meclizine, dimenhydrinate, diphenhydramine, and promethazine. Choice of medication is based on trip duration, underlying medical problems, and concerns about sedation. Scopolamine patches are appropriate for longer voyages and should be applied 4 hours before departure and changed every 3 days if needed. Oral scopolamine is effective for 68 hours and can be used for short journeys or for the interval between application of the patch and onset of effectiveness. Other oral medications are efficacious for several hours and can also be used for shorter journeys. All oral medications should be started 1 hour before departure. All these medications can impair alertness and must be used with caution by those operating vehicles or heavy machinery. This effect is additive with alcohol and is least severe with scopolamine. In addition, all have anticholinergic properties and should be avoided in travelers with narrow-angle glaucoma, pyloric obstruction, or prostatic hypertrophy and used with caution in those with asthma and cardiovascular disease. Side effects include dry mouth, blurred vision (especially for persons with hyperopia), and bradycardia. Promethazine primarily decreases nausea and has been combined with ephedrine (2550 mg) to decrease sedation. Only dimenhydrinate and diphenhydramine are recommended for use in children. They may cause paradoxical excitation and should not be used in children <2 years of age.

Nonpharmacologic methods for motion sickness may benefit some persons but have not been proven to have consistent efficacy. High levels of ginger have been helpful in some persons. Pressure on the P6 acupuncture point of the wrist provides relief of nausea in pregnancy and after chemotherapy, but evidence for efficacy in motion sickness is contradictory.

Dosages of anti-motion sickness medications
Medication Dose Contraindications Adverse effects Comments
Scopolamine

Patch: change every 72 hours. Apply to hairless area behind ear.

Oral: 0.40.8 mg every 68 hrs

Gastrointestinal or bladder neck obstruction (e.g., prostatic hypertrophy), liver or kidney disease, risk for acute-angle glaucoma Dry mouth, bradycardia, blurred vision (especially in hyperopic persons), decreased memory for new information, decreased attention and alertness Useful for longer journeys. Do not touch eyes after applying patch. Contraindicated in children.
Dimenhydrinate

Adult: 2550 mg up to 4 times per day

Children: 1.25 mg/kg, up to 25 mg. Can be repeated every 6 hrs

Use with caution in persons with asthma, cardiac arrhythmias, pyloric or bladder neck obstruction, narrow-angle glaucoma Drowsiness, thickened respiratory secretions, dry mouth, blurred vision, paradoxical excitation in children  
Diphenhydramine

Adult: 2550 mg up to 4 times per day

Children: 1 mg/kg, up to 25 mg

As for dimenhydrinate As for dimenhydrinate  
Promethazine Adult: 2550 mg up to 4 times per day As for dimenhydrinate As for dimenhydrinate; hypotension, abnormal movements

May be combined with ephedrine to help maintain alertness. Primarily controls nausea.

Not recommended for children.

Meclizine 2550 mg daily Asthma, narrow-angle glaucoma, bladder neck obstruction Drowsiness, dry mouth, occasional blurred vision Not recommended for children.

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Motion Sickness