Preventing motion sickness in children

Motion sickness is a normal response to abnormal stimuli. The peak incidence occurs in children under 12 years, but it is uncommon in infants. As this condition has central and vestibular origins, centrally acting drugs may be useful. There is no evidence to support the efficacy or safety of drugs for children less than two years old. Potentially effective drugs in older children include hyoscine and antihistamines. Both are associated with anticholinergic adverse effects. Ginger and acupuncture bands may be used, but have only been evaluated in adults.

Motion sickness is a common condition, with about 30% of the general population suffering some kind of symptoms during a voyage and 5% suffering heavily. There are no specific statistics for incidence in children. Children under two years old are highly resistant to motion sickness, as they are often supine and do not use visual cues for spatial orientation. Susceptibility peaks around 10–12 years of age. Motion sickness in children occurs mainly during car, train and air travel, but also may occur on amusement park rides and during virtual reality immersion.¹

There are simple preventative measures which may reduce the likelihood of travel sickness (see box). If these fail, pharmacological therapies may be tried in children older than two years.

Conflicting signals from vestibular, vision and proprioception systems produce symptoms of pallor and cold sweat, which usually precede epigastric discomfort, nausea and emesis. Ataxia and dizziness may be a feature in younger children. Prolonged motion sickness may cause drowsiness, apathy and even a feeling of impending doom. Cortical centres may also be involved, explaining the effect of anticipatory nausea before travelling.

The first mention of a drug for motion sickness was in the 1860s in the Lancet, when tincture of belladonna was recommended.

Promethazine was approved in the 1950s, but it is only since the 1970s that cholinergic stimulation has been the postulated basis of motion sickness. Primarily, antihistamines and anticholinergics are used. These drugs act on vestibular receptors and nuclei, the cerebellum and the vomiting centre.

The following general points should be considered when managing children who are prone to motion sickness:

• As motion sickness induces gastric stasis, it slows drug absorption, so preventing symptoms from occurring is more effective than trying to treat them after symptom onset.
• There are no controlled studies of anti-motion sickness drugs in young children. Clinical use is based on pharmacology principles and extrapolation of data from adult studies.
• While most anti-motion sickness medicines cause drowsiness, they should not be used as sedatives for air travel, as excessive sedation combined with lower oxygen partial pressure can be potentially dangerous for some children.³
• All anti-motion sickness medications are also effective antiemetics.

Efficacy and safety

Hyoscine hydrobromide (scopolamine)

A systematic review of 14 controlled trials involving hyoscine found it to be more effective than placebo, but not superior to antihistamines. Studies were predominantly in adult males. Hyoscine is less sedating than antihistamines, but has more anticholinergic effects.⁵

Antihistamines

Given their lack of efficacy and potential to cause serious adverse drug reactions, such as hallucinations, agitation and breathing difficulties, antihistamines (H1 receptor antagonists) should not be used to prevent or treat motion sickness in children less than two years of age and should be used with caution in older children. Fatalities have been reported when over-the-counter products containing antihistamines were given to young children to treat coughs and colds.⁶ There are no specific paediatric data for these drugs in motion sickness and dosing has been extrapolated from studies done in adults. In Australia, sedating antihistamines have recently become prescription-only for children less than two years of age.⁷ This is now in line with New Zealand regulations. These drugs cause anticholinergic adverse effects of excitability, agitation, drowsiness, dry mouth, blurred vision and constipation. They should be avoided in children with seizure disorders.

Promethazine theoclate, promethazine hydrochloride and dimenhydrinate are approved in Australia for prevention and treatment of motion sickness. Timing varies, but they should be given at least 30 minutes before travelling. While diphenhydramine is used overseas for motion sickness prophylaxis in children, this is not an approved indication in Australia.

Non-sedating antihistamines, such as loratadine and cetirizine, penetrate poorly into the central nervous system and are not effective against motion sickness.

Complementary alternatives

Studies in adults using acupuncture wristbands, which activate the P6 Neiguan acupuncture point (5 cm above the wrist), show relief of nausea in pregnancy and after chemotherapy, but evidence for efficacy in motion sickness is contradictory. There are no studies in children, although wristbands are marketed for this age group.

Placebos have provided benefit in up to 45% of cases in controlled studies.⁸

Ginger (Zingiber officinale) has been used for centuries for its antiemetic properties.⁹ Studies have shown reduced nausea in patients with hyperemesis gravidarum, postoperative nausea and vomiting and in a study using a revolving chair simulating motion sickness. There has not been more than anecdotal evidence of the efficacy of ginger for prevention and treatment of motion sickness in children. Ginger inhibits thromboxane synthetase and in high doses may potentiate the effects of anticoagulants, for example aspirin, heparin and warfarin. It may cause mild gastrointestinal upset.

A study using prism glasses from the 1980s reported a significant decrease in vomiting episodes in children (n=201) prone to motion sickness. The prism glasses were thought to decrease the discrepancy between visual and vestibular cues and thus to reduce the negative effects of vertigo.¹⁰

Treatments available overseas^2,11

Hyoscine as a transdermal patch is available overseas for children older than 10 years. These patches have been shown to provide effective motion sickness prophylaxis for 72 hours, but have not been evaluated in younger children. Toxic psychosis has been reported in children using this treatment.

Cinnarizine and its derivative flunarizine are piperazine antihistamines with vasodilating actions of calcium channel blockers. The only study of anti-motion sickness drugs specifically in children was in an open study with cinnarizine. It was rated by participants (n=79, mean age 8.4 years) to be effective in preventing car sickness, with a low level of adverse effects.¹²

Motion sickness is a common condition, with many marketed remedies for children. Few have undergone controlled trials and even fewer have been scientifically tested specifically in children. The recent changes in labelling and restriction of access of antihistamines for children younger than two years of age highlight the importance of continual review of medicines used in children.

Acknowledgement: Dr Madlen Gazarian, Paediatric Clinical Pharmacologist and Head, Paediatric Therapeutics Program, University of New South Wales and Sydney Children's Hospital, for helpful comments about the manuscript.

The following statements are either true or false.

1. Children travelling by plane should not be sedated with antihistamines.

2. To prevent motion sickness, medication should be given at least 30 minutes before the start of a journey.

Answers to self-test questions

1. True

2. True