Motion Sickness Causes, Epidemiology, Symptoms, Treatment and Additional advices.

Motion sickness
Causes
Motion sickness is a form of vertigo in which autonomic symptoms predominate.
The cause is thought to be disturbance of the vestibular apparatus of the inner ear, which controls balance, brought on by unaccustomed types of movement. During travel confl icting stimuli are received in the brain from the eyes and remembered experience of usual forms of movement, such as walking. This sensory mismatch is interpreted as a noxious stimulus and initiates a physiological response similar to that to substances perceived as poisonous, and a number of autonomic nervous system responses are activated to reject the perceived poison.
The body adapts to unfamiliar types of motion on prolonged or repeated exposure, explaining why seasickness, for example, tends to subside after a few days.
Epidemiology
Motion sickness is more common in women than men.
It is uncommon in children under 2 years and most common in children between 2 and 12, reaching a peak at 12 years. Incidence reduces thereafter and after 21 declines signifi cantly with age.
Women are more susceptible during menstruation and pregnancy.
Signs and symptoms
Muscarinic effects, including:
nausea
vomiting
increased salivation
general malaise
pallor
sweating
yawning
hyperventilation.
Gastric motility is also reduced and digestion impaired.
Differential diagnosis
Nausea and vomiting occur in a wide range of conditions, but the symptoms of motion sickness are usually very clearly associated with travel. Patients will nearly always ask for advice on prevention rather than treatment of current symptoms.
Treatment
Sedating antihistamines and hyoscine are licensed for use without prescription for prophylaxis and treatment of motion sickness. They appear to be of more or less equivalent effi cacy.
They are effective for prevention, but use for treatment is often unsuccessful as vomiting and gastric stasis prevent or substantially reduce their absorption. Hyoscine
Hyoscine competitively inhibits the actions of acetylcholine at the muscarinic receptors of autonomic effector sites innervated by parasympathetic nerves. It has a central as well as a peripheral action, as it is lipid-soluble and crosses the blood–brain barrier.
Sedating antihistamines
The older (fi rst-generation) antihistamines which tend to cause sedation have antimuscarinic side-effects similar to the actions of hyoscine. (Second-generation antihistamines, which generally do notcause drowsiness, do not exert antimuscarinic side-effects and are of no use for motion sickness.)
Sedating antihistamines licensed for the treatment of motion sickness (all P medicines) are:
cinnarizine
meclozine
promethazine hydrochloride
promethazine teoclate.
  The length of action, degree of sedation and side-effects vary between the antihistamines
Side-effects and cautions: hyoscine and antihistamines
Hyoscine and antihistamines exhibit the same range of side-effects. However, side-effects tend to be more pronounced with hyoscine, and include:
dry mouth
blurred vision
urinary retention
constipation
sedation (more marked with antihistamines).
Both hyoscine and antihistamines should be avoided in patients suffering from glaucoma or prostatic hypertrophy, are not recommended for use by pregnant or breastfeeding women, and should be used with caution in the elderly and patients with epilepsy or cardiac or cardiovascular disease.
Hyoscine and sedating antihistamines increase the effects of other drugs that cause sedation or have antimuscarinic actions, including many antidepressants and antipsychotic agents.
  Alcohol should be avoided when taking medication against motion sickness.
 
Additional advice
There are several things that people can do to minimise the chance of suffering from motion sickness on journeys.
General
Avoid heavy meals before travelling.
Avoid pungent odours.
Avoid alcohol.
Road travel
Drive, if possible, as drivers very rarely suffer from motion sickness.
If you do not or cannot drive, sit in the front passenger seat if possible.
Sit near the front in a bus or coach.
Keep vehicle windows open.
Do not try to read, and keep looking out of the window. Distract children with games such as I Spy, to make them look out.
Listen to the radio or talk with other passengers.
Sea travel
If possible, stay on deck and keep eyes fi  xed on the horizon.
Below deck, stay in the centre of the ship and lie down with eyes closed.
Air travel
Try to sit by the wing.