"Stop the car, Mom, I'm going to be sick!"

By William M. Stauffer, MD, Robert J. Konop, PharmD, Gregory A. Plotnikoff, MD, and Deepak Kamat, MD, PhD

Parents often ask for help with their child's motion sickness, a condition that has become increasingly common. Is prescribing an antihistamine or a complementary therapy a good idea? Or is prevention the best route? This rundown of possible strategies will help you decide.

Motion sickness is becoming increasingly familiar to parents and pediatricians. This malady, which is characterized by nausea and other uncomfortable symptoms induced by passive or perceived movement, is nothing new. In fact, the word "nausea" derives from the Greek word "naus," which means ship, indicating that motion sickness was recognized thousands of years ago. The increase in travel by different modes of transportation (not just boats), the prevalence of amusement parks with their stomach-lurching rides, and the popularity of video games have increasingly led parents to ask: "What can you do to help my child with motion sickness?"

It's not easy to answer this question because literature based on evidence-based medicine is lacking—at least with regard to children. Nonetheless, a review of accepted strategies to prevent and treat motion sickness in infants and children should be helpful. Although use of pharmacologic agents is most common, alternative therapies also are available. We believe these therapies on the whole, when used appropriately, may be preferable to drugs because of their very small risk of side effects, if any.

Who has motion sickness and why?

The pathophysiology of motion sickness, described in the "What causes motion sickness?" box, is extremely complex and not well understood. The condition is common, with 58% of children reportedly experiencing car sickness.¹ Even though motion sickness is usually nothing more than a minor nuisance, it can be incapacitating.² Certain factors have been associated with motion sickness:

• Age between 4 and 10 years. Children under the age of 2 years rarely experience motion sickness.³

• Female gender. Regardless of age, boys are less susceptible than girls.^1,4

• Consumption of dairy products and foods high in sodium, protein, and calories.⁵

• Emotional upset, ear infections, and noxious stimuli, such as environmental smoke, which can aggravate symptoms of motion sickness.⁶

• Oral contraceptives, which enhance motion sickness in teenage girls, who are also more likely to experience motion sickness during a menstrual period.⁷

• Low-frequency motion, such as the swaying of a boat. This type of movement is more likely to induce motion sickness than movement that is more vigorous.¹

In adults, motion sickness is well characterized as epigastric discomfort, nausea, vomiting, drowsiness, headache, and generalized discomfort. The most common presenting symptom of motion sickness in children younger than 5 years, however, is ataxia, while nausea prevails in children older than 12.⁸ In one study of children 4 to 15 years of age in whom motion sickness was evoked, those in kindergarten had marked gait abnormalities, including falls, but only minimal symptoms related to the autonomic nervous system. The frequency and severity of sickness gradually increased during growth as autonomic symptoms became more pronounced; the gait abnormalities became less severe, however. Investigators attributed this discrepancy to the poorly developed perception of spatial orientation of younger children as well as the immaturity of their vestibular system (which relates to maintenance of equilibrium), which led to the gait abnormalities that moderated as the children matured.⁹ Other symptoms of motion sickness commonly seen in children are vomiting, pallor, vertigo, and cold sweats. Unfortunately, vomiting does not relieve the other symptoms of motion sickness.⁶

How to treat motion sickness

The most specific targets of antimotion sickness medications are the vestibular nuclei because vestibular stimuli are critical in the generation of motion sickness. Developing drugs for motion sickness has been difficult because of the multiple neurotransmitters and stimulatory and inhibitory receptors on the vestibular nuclei. Not knowing the precise pathway of motion sickness also complicates matters. Available agents generally target dopamine and acetylcholine activity, as these neurotransmitters have been most implicated in the pathophysiology of motion sickness.

Antihistamines are used more frequently than any other type of drug for preventing motion sickness. Their duration of action is longer, and they are considerably safer than other drugs. These agents produce varying degrees of sedation. It is not known why antihistamines have an effect on motion sickness. It could be because they act on the histamine receptors of the vestibular nuclei, because of their nonspecific suppression of the neurons, or because of the agents' anticholinergic properties. In addition to feeling tired and having other common side effects of antihistamines (dry mouth, constipation, and blurred vision), children may have a paradoxical reaction to these drugs. Warn parents about this before starting treatment.

Dimenhydrinate (Dimentabs, Dramamine, Dramilin) contains equimolar proportions of diphenhydramine and chlorotheophylline. It is widely used for preventing motion sickness in adults and children. The most pronounced side effect of dimenhydrinate is drowsiness. It also has been implicated in impeding the diagnosis of treatable conditions associated with vomiting, such as appendicitis in children, because it suppresses vomiting.¹⁰ Dimenhydrinate is available in tablet, liquid, parenteral (intramuscular [IM], intravenous [IV]), and chewable tablet forms. A rectal form is not available in the United States. The extended-release formulation should not be used in children. The dosage is 5 mg/kg/d, given in four divided doses, with a maximum dosage of 400 mg/d.

Diphenhydramine hydrochloride (Benadryl) is also commonly used for preventing motion sickness in adults and children. As with dimenhydrinate, the major side effect is drowsiness, though the agent also can cause dizziness and thickening of bronchial secretions. Diphenhydramine is available in tablet, syrup, and parenteral (IM, IV) formulations. The dose is 1 mg/kg taken every four to six hours as needed (maximum dose is 25 to 50 mg). Diphenhydramine should be taken at least 30 minutes (and preferably one to two hours) before exposure to a situation expected to induce motion sickness.

Meclizine hydrochloride (Antivert, Bonine) is longer acting than other antihistamines. It has not been studied in children younger than 12 years. Children are known to be especially sensitive to anticholinergics, which are pharmacologically related to meclizine. Common side effects include drowsiness, blurred vision, and dryness of the mouth, nose, and throat. Meclizine is contraindicated for children with chronic lung diseases such as asthma. The dose for children older than 12 years is 12.5 to 25 mg orally one hour before travel with repetition of the same dose every 12 to 24 hours.

Anticholinergics. Scopolamine (Hyoscine, Transderm Scop) is the most extensively used anticholinergic agent. Scopolamine nonselectively inhibits all five muscarinic receptors. It should not be used in children younger than 12 years of age because clinical data are lacking and because these youngsters are more susceptible to belladonna alkaloids than those who are older. For children older than 12 years the dose is one patch, which contains 1.5 mg of scopolamine hydrochloride. The patch is usually applied to intact skin behind the ear and has to be replaced every 72 hours. If the agent is used for long periods of time, it may cause symptoms such as headache, nausea, and dizziness upon withdrawal. Common adverse drug reactions include dry mouth, dry skin, blurred vision, difficulty urinating, constipation, and tachycardia.

Phenothiazines. Promethazine (Anergan, Phenergan) is a phenothiazine derivative. Its antidopaminergic activity is extremely weak, but its antimuscarinic and antihistamine activity are considerably stronger. This makes prometh- azine useful for preventing and treating motion sickness; it also is effective against other emetic stimuli. Adverse events associated with promethazine include sedation, blurred vision, lowering of the seizure threshold, and dystonic reactions. (Dystonic reactions caused by phenothiazines are treated with diphenhydramine.) Promethazine should be administered with food to decrease GI irritation. It is available in syrup, tablet, suppository, and injectable forms. The pediatric dosage is 0.5 mg/kg taken orally 30 to 60 minutes before leaving on a car trip, for example, and then every 12 hours as needed. An advantage of promethazine is that it has been used extensively, both intramuscularly and as a suppository, for treating motion sickness. Promethazine should not be used in children younger than 2 years because of a possible association with sudden infant death syndrome and sleep apnea.¹¹

Dopamine antagonists. Metoclopramide (Reglan) and prochlorperazine (Compazine) are not recommended in children because they are not effective against motion sickness in adults. In addition, prochlorperazine has been associated with a high incidence of extrapyramidal side effects in children, such as tremors, rigidity, opisthotonus, torticollis, and oculogyric crisis.¹²

Table 1 summarizes the drugs used to treat motion sickness in children. Table 2 describes the pathways through which various classes of drugs work.

TABLE 1
Drug treatment of motion sickness

TABLE 2
Pathways for drug treatment of motion sickness in children

Management without drugs

Parents are increasingly interested in "more natural" or "less toxic" options for treating their children's motion sickness. Evidence for nonpharmaceutical therapies is most frequently found for traditional or adult uses. Few randomized controlled clinical trials of such therapies have been conducted in children. Nonetheless, we recommend considering simple and safe nonpharmaceutical options such as acupressure and ginger before using drugs, which often have at least some side effects. In addition, certain drugs, such as meclizine and scopolamine, have not been studied in or recommended for patients under the age of 12 years.

Ginger root (Zingiber officinale) is the most widely recognized complementary therapy for motion sickness. Ginger root is readily available in different forms (capsule, powder, candy, or tea), and the use of ginger ale for nausea and abdominal pain is based on a traditional belief in the efficacy of ginger. (However, few ginger ale sodas commercially sold today actually contain ginger.) Ginger root has been evaluated by the German government's Commission E (comparable to the US Food and Drug Administration) and has been approved for use in prevention of travel sickness symptoms. The active ingredients in ginger are believed to be 6-gingerol and a galanolactone, but their precise mechanism of action is not well understood. Ginger root has shown mixed results as an antimotion sickness agent, but no adverse effects were reported.^13,14 Traditional dosing for adults and children older than 12 is 1,000 mg per day (taken one hour before traveling) or 250 mg orally four times a day. This dose is reduced by half for children 6 to 12 years of age and by three quarters for children 3 to 6 years of age.

Nontoxic teas also are recommended in lay literature available to parents—in magazines, for instance, or over the World Wide Web. These teas contain anise seed (Anisis fructus), chamomile flowers (Matricariae flos), or meadowsweet (Filipendula ulmaria),¹⁵ or are made from a tincture containing sweet sedge (Acorus calamus), sweet woodruff (Asperula odorata), or wormwood (Artemisia absinthium).¹⁶ (Wormwood is toxic if ingested chronically.) These herbs are among the 30 plants Commission E monographs cite for treating loss of appetite, indigestion, or other dyspeptic symptoms, but they have not been tested for motion sickness. Other therapies for gastric distress noted for adults include apricot juice, carrot juice, raw pumpkin or squash seeds, crushed parsley, and peppermint tea.¹

Acupressure and acupuncture are the best-studied nonpharmaceutical interventions for both adults and, by extrapolation, for children. Classically, stimulation of the Neiguan (P6) meridian point on the wrists produces antiemetic effects in patients who are awake. In adults, this point is approximately 3 cm from the distal palmar crease between the palmaris longus and flexor carpi radialis tendons (see figure). Many studies in adults have shown positive effects of acupressure or acupuncture antiemetic prophylaxis in perioperative settings.^17,18 Two studies of Neiguan wrist massage of P6 using wrist bands showed mixed results.^19,20 A single study demonstrated the effectiveness of a portable acustimulation device in controlling seasickness.²¹

Results of investigations in children were mixed. Two studies in children undergoing strabismus surgery have demonstrated marked reduction in postoperative vomiting with P6 or K-K9 point stimulation.^22,23 (The Korean hand acupuncture point K-K9 is located on both hands on the palmar surface of the middle phalanx of the fourth finger. It corresponds to the Chinese P6 point, but at a different location.) A well-designed study of acupressure-acupuncture antiemetic prophylaxis in children undergoing tonsillectomy demonstrated no reduction in vomiting compared with placebo.²⁴

Self-regulation training. Recently, training in self-regulation of the autonomic nervous system was shown to be superior to promethazine.²⁵ Behavioral pediatricians frequently provide this training for a variety of other medical concerns, including asthma, headaches, and functional abdominal pain. Using specially designed and commercially available video-game technologies for biofeedback therapies, most children older than 6 years can develop significant skills in self-regulation.^26,27

Table 3 summarizes alternative therapies for motion sickness.

TABLE 3
Nonpharmaceutical treatment of motion sickness

Practical strategies

Nonpharmaceutical interventions for motion sickness, particularly behavioral interventions, are not practical for very young children, who are not old enough to follow commands and suggestions. The effectiveness of behavioral interventions will depend on the developmental stage of the child.

Certain measures taken before or during traveling can help prevent motion sickness. Parents can help their child to do the following.

Before traveling:

• Eat a light meal at least three hours before leaving

• Avoid dairy products (use juices instead) and foods high in sodium, protein, or calories

While traveling:

• Sit in the front seat of a car (but only when the child's size and age make this a safe place)

• Focus on a stable horizon or object while moving

• Avoid visual stimuli (reading books, playing video games)

• Increase ventilation or exposure to cool, fresh air

• Lie on the back whenever possible and limit head movement by placing the head on a stable object

Putting it together

Many children suffer motion sickness, but few antimotion sickness agents with sufficient experience or efficacy trials are available for them for routine use. Whenever possible, we recommend using nonpharmaceutical measures. When a family does plan on using a drug, prescribe the agent in a test dose before a trip to determine if the child will have a paradoxical response or other side effect. Antihistamines, particularly dimenhydrinate and diphenhydramine, are the best agents for children because they have few side effects, are long acting, and have the greatest clinical experience. Promethazine can be used in children for preventing as well as treating motion sickness. The advantage of this agent in a child with vomiting is that it can be given intramuscularly or rectally. In view of the data currently available and known adverse effects, scopolamine should not be used in children younger than 12 years.

REFERENCES

1. Gahlinger PM: Motion sickness: How to help your patients avoid travel travail. Postgrad Med 1999; 106(4):177

2. James M, Green R: Airline incapacitation survey. Aviat Space Environ Med 1991;62(11):1068

3. Benson AJ: Motion sickness, in Stellman JM (eds): Encyclopedia of Occupational Health and Safety, ed 4. Geneva: International Labour Office, 1998:50.12

4. Dobie T, Mcbride D, Dobie T Jr, et al: The effects of age and sex on susceptibility to motion sickness. Aviat Space Environ Med 2001;72(1):13

5. Lindseth G, Lindseth PD: The relationship of diet to airsickness. Aviat Space and Environ Med 1995; 66(6):537

6. Wilderness medicine management of wilderness and environmental emergencies, in Auerbach PS (ed): St. Louis Mosby-Year Book, ed 3, p 478

7. Kozarsky PE: Prevention of common travel ailments. Infect Dis Clin North Am 1998;12(2):305

8. Takahashi M, Ogata M, Miura M: The significance of motion sickness in the vestibular system. J Vesib Res 1997;7:179

9. Takahashi M, Toriyabe I, Takei Y, et al: Study on experimental motion sickness in children. Acta Oto-Laryngologica 1994;114(3):231

10. Anquist KW, Panchanathan S, Rowe PC, et al: Diagnostic delay after dimenhydrinate use in vomiting children. CMAJ 1991;15(8):965

11. Stanton AN: Sudden infant death syndrome and phenothiazines. Pediatrics 1983;71:986

12. Pesola GR: Neurologic complications of prochlorperazine. Ann Emerg Med 1998;31(2):285

13. Stewart JJ, Wood MJ, Wood CD, et al: Effects of ginger on motion sickness susceptibility and gastric function. Pharmacology 1991;42:111

14. Ernst E, Pittler MH: Efficacy of ginger for nausea and vomiting: A systemic review of randomized clinical trials. Br J Anaesth 2000;84:367

15. Bove M: An Encyclopedia of Natural Healing for Children and Infants. New Canaan, Conn., Keats Publishing, 1996

16. Scott J: Natural Medicine for Children: Drug-Free Health Care for Children from Birth to Age 12. New York, William Morrow, 1990

17. Al-Sadi M, Newman B, Julius S: Acupuncture in the prevention of postoperative nausea and vomiting. Anaesthesia 1997;52:658

18. Fac CF, Tanhui E, Joshi S, et al: Acupressure treatment for prevention of postoperative nausea and vomiting. Anesth Analg 1997;84:821

19. Bruce DG, Goldig JF, Hockenhull N: Acupressure and motion sickness. Aviat Space Environ Med 1990;61:361

20. Hu S, Stritzel R, Chandler A: P6 acupressure reduces symptoms of vection-induced motion sickness. Aviat Space Environ Med 1995;6:631

21. Bertolucci Le, DiDario B: Efficacy of a portable acustimulation device in controlling seasickness. Aviat Space Environ Med 1995;66:1155

22. Schlager A, Offer T, Baldissera I: Laser stimulation of acupuncture P6 reduces postoperative vomiting in children undergoing strabismus surgery. Br J Anaesth 1998;81:529

23. Schlager A, Boehler M, Puhringer F: Korean hand acupressure reduces postoperative vomiting in children after strabismus surgery. Br J Anaesth 2000;85:267

24. Shenkman Z, Holzman RS, Kim C, et al: Acupressure-acupuncture antiemetic prophylaxis in children undergoing tonsillectomy. Anesthesiology 1999; 90:1311

25. Cowing PS, Toscano WB: Autogenic-feedback training exercise is superior to promethazine for control of motion sickness symptoms. J Clin Pharm 2000; 40(10):1154

26. Culbert TP, Kaajander RL, Reaney JB: Biofeedback with children and adolescents: Clinical observations and patient perspectives. J Dev Behav Paediatr 1996;17:342

27. Olness K: Cyberphysiologic strategies in pediatric practice (biofeedback, self-hypnosis and relaxation training). Pediatr Ann 1991;20:115

DR. STAUFFER is staff physician, Regions Hospital, internal medicine and pediatrics, Center for International Health & International Travel Clinic, St. Paul, Minn., and a fellow, pediatric emergency medicine, University of Minnesota, Minneapolis.

DR. KONOP is senior clinical pharmacist, Prime Therapeutics, Eagan, Minn.

DR. PLOTNIKOFF is associate professor, clinical medicine and pediatrics, University of Minnesota, and medical director, Center for Spirituality and Healing, Minneapolis.

DR. KAMAT is professor, department of pediatrics, West Virginia University, Morgantown.

What causes motion sickness?

Advocates of the so-called sensory conflict theory of motion sickness believe that this malady develops when information from the eyes, the vestibular system (which helps us keep our balance), and nonvestibular proprioceptors indicate that our bodies are in a different position from the one that past experiences would lead us to expect.^1­3 Sensory conflict, these observers believe, even accounts for motion sickness evoked by visual stimuli alone, such as watching a panoramic movie: The vestibular system perceives that the head is stable while the visual system perceives that the head is moving.³ It recently has been shown that other sensory inputs, such as signals from visceral graviceptors (receptors in organs that give the brain information about body position, equilibrium, and direction of gravitational forces) may also contribute to motion sickness.⁴

In humans, the vestibular system and the visual system are the two principal sensory systems that perceive movement of the body in space. That people who are blind suffer motion sickness indicates that the visual system is not necessary for producing motion sickness.⁵ The vestibular system is essential, however; we know this because individuals with bilateral vestibular dysfunction do not experience motion sickness even when appropriate stimuli are applied.⁶ The semicircular canals and the otolith organs, both of which are located in the labyrinth in the inner ear, are the end organs of the peripheral vestibular system. The semicircular canals detect head movement in any direction while the otolith organs provide information about the head position with respect to gravity.

Many neurotransmitters and neuromodulators, such as histamine, acetylocholine, norepinephrine, and serotonin, have been shown to participate in the activity of vestibular nuclei. There is extensive convergence of vestibular and nonvestibular afferent information in the brainstem. Humans who have had portions of their brain removed can develop motion sickness with appropriate stimuli, indicating that the brainstem has the necessary neurocircuits to generate motion sickness.⁷ The brainstem controls the somatic and autonomic motor activity associated with motion sickness. The chemoreceptor trigger zone of the medulla oblongata is stimulated by high levels of dopamine, produced in response to sensory conflict, which in turn stimulates the vomiting center within the reticular formation of the brainstem.⁸

The motor pathway for the final act of motion sickness—namely, vomiting—includes complex activities of the gastrointestinal tract and the respiratory apparatus. Vomiting is preceded by nausea, the most prominent symptom of motion sickness. A 20- to 30-fold rise in plasma vasopressin levels, resulting in elevated blood pressure, contraction of the intestinal musculature, and increased peristalsis, has been reported at the onset of nausea, although not everyone with nausea has an elevated vasopressin level.⁹ Autonomic symptoms of motion sickness, such as cold sweating, salivation, and pallor, are produced by selective activation of the components of the sympathetic and parasympathetic system.¹⁰

REFERENCES

1. Bles W, Bos JE, De Graaf B, et al: Motion sickness: Only one provocative conflict? Brain Res Bull 1998;47:481

2. Oman CM: Sensory conflict theory and space sickness: Our changing perspective. J Vest Res 1998;8:51

3. Oman CM: Motion sickness: A synthesis and evaluation of the sensory conflict theory. Can J Physiol Pharmacol 1990;68:294.

4. Mittelstaedt H: Somatic graviception. Biol Psychol 1996;42:53

5. Graybiel A: Susceptibility to acute motion sickness in blind persons. Aerospace Med 1970;41:650

6. Cheung BS, Howard IP, Money KE: Visually induced sickness in normal and bilaterally labyrinthine defective subjects. Aviat Space Environ Med 1991;62: 527

7. Doig RK, Wolf S, Wolff HG: Studies of gastric function in a "decorticate" man with gastric fistula. Gastroenterology 1953;23:40

8. Gahlinger PM: Motion sickness: How to help your patients avoid travel travail. Postgrad Med 1999;106(4):177

9. Koch KL, Summy-Long J, Bingaman S, et al: Vasopressin and oxytocin responses to illusory self-motion and nausea in man. J Clin Endocrinol Metab 1990;71:1269

10. Cowings PS, Naifeh KH, Toscano WB: The stability of individual patterns of autonomic responses to motion sickness stimulation. Aviat Space Environ Med 1990;61:399

Effect of antimotion medications on breast milk

Little data are available on the excretion in breast milk of most of the medications used to treat motion sickness in adults.¹ The American Academy of Pediatrics considers scopolamine compatible with breastfeeding. Because it is known that infants have an increased sensitivity to antihistamines, breastfeeding mothers should use these agents with caution.¹ Pediatricians need to educate breastfeeding mothers about this issue.

REFERENCE

1. Paton DM, Webster DR: Clinical pharmacokinetics of H₁-receptor antagonists (the antihistamines). Clin Pharmacokinet 1985;10:477

GUIDE FOR PARENTS

When your child has motion sickness

If your child becomes nauseated when she (or he) rides in a car, she has a lot of company. More than half of all children become carsick, and many others experience motion sickness (as this condition is called) when they travel in a plane or boat, go on an amusement park ride, play a video game, or watch a panoramic movie. Children between the ages of 4 and 10 years are most likely to be affected by motion sickness; those younger than 2 years are least likely to have it. Girls are more susceptible to motion sickness than boys. Motion sickness may also cause vomiting, pale skin, dizziness, cold sweats, or, in children younger than 5 years, an irregular gait.

Doctors and scientists do not know exactly what causes motion sickness. They believe it develops when the sensations we receive from our eyes and the part of the brain that helps us keep our balance do not match what the brain believes the actual position of the body should be.

If your child suffers from motion sickness, you should talk to your physician about it. He or she may prescribe a medicine that will prevent this condition. You might also want to ask the doctor about alternative therapies that don't rely on drugs: drinking certain teas, acupressure, or a behavioral training technique known as self-regulation.

You can also minimize the likelihood that your child will suffer motion sickness by following these simple guidelines:

• When traveling by plane or ship, request seats at the center of the craft.

• Give your child a light meal three hours or more before traveling. Avoid dairy products and foods high in protein, calories, and salt. Also give the child light meals during the trip.

• Your child may have less motion sickness in the car if she sits in the front seat. But keep in mind that if your child is younger than 12 years, she will be most safe riding in the back seat. If your child is under the age of 1 year, never put her in the front seat of the car.

• Use a booster seat so the child can look outside and focus on an external object, which helps to prevent motion sickness. Have the child face in the direction you are traveling (unless she is an infant and must be in a backwards-facing seat).

• Increase the ventilation or exposure to cool fresh air. If you are traveling in a car, stop frequently and get out of the car.

• Do not let your child read books, watch TV, or play hand-held electronic games while traveling.

• Limit your child's head movements by asking her to lay her head on an object that remains stable.

• When traveling in a ship or a train, encourage your child to lie on her back.

This guide may be photocopied and distributed without permission to give to your patients and their parents. Reproduction for any other purpose requires express permission of the publisher.