OTC MEDICINES
Over-the-counter remedies are less effective than prescription-strength medications, but provide a lesser degree of side effects and long duration of 6 to 12 hours. (20). These must be taken at least an hour before exposure to be effective, since gastric motility decrease following the onset of motion sickness.(9) These can be useful for travelers who experience mild to moderate cases of motion sickness. Most of these (remedy) medications are antihistamines, and their initial use stemmed from reports that people being treated for allergies also experienced fewer problems with motion sickness. Although it is unclear precisely how they work to suppress motion sickness symptoms, their anticholinergic properties appear to be the important element.(21)
Anecdotal reports indicate large individual differences in the effectiveness of antihistamines as antimotion sickness drugs. Dimenhydrinate (Dramamine) appears to be the most effective. The usual adult dosage is 50 mg, which typically produces some drowsiness and minor dizziness. (9) It is not recommended when driving or working around machinery, but can be a good choice for long exposure to mild-to-moderate motion.(18)
Cyclizine (Marezine) is somewhat less effective at the usual adult dosage of 50 mg, but causes less drowsiness and dizziness and is often used to avoid travel sickness in children or very mild short-term exposures to motion in adults. (9) When Weinstein et al compared cyclizine and dimenhydrinate in a study involving 5 college students deemed susceptible to motion sickness, they found that the two are similarly effective in preventing the overall subjective symptoms of motion sickness, such as dizziness, sweating, and nausea. Marezine, however, was associated with more improvement of GI symptoms and with significantly less drowsiness than dramamine 30 minutes after ingestion (22, 23)
Meclizine (Bonine, Antivert) has a slower onset and longer duration (12 to 24 hours) of action than the other antihistamines. The slower onset may be why it also has a lower efficacy rating. Side effects include drowsiness, dry mouth, blurred vision, and dizziness. (9)