Antihistamines are among the most commonly used medicines to reduce the symptoms of motion sickness. They block motion signals to the brain. These medicines include:

• Dimenhydrinate (such as Dramamine).
• Diphenhydramine (such as Benadryl).
• Meclizine (such as Antivert and Bonine tablets).
• Trimethobenzamide (such as Tigan).
• Cinnarizine.

The medicines can be taken before travel and repeated during extended travel according to the directions on the package.

Drowsiness is the main side effect of antihistamines. In children, antihistamines can have the opposite effect, making children excited rather than sleepy. Antihistamines can also cause dizziness. Don't give antihistamines to your child unless you've checked with the doctor first.

• People who have emphysema or other breathing difficulties or glaucoma should consult a doctor before taking antihistamines.
• People who have asthma, high blood pressure, hyperthyroid disease, or cardiovascular disease should consult a doctor before taking antihistamines.

Dimenhydrinate, diphenhydramine, and some preparations of meclizine (such as Bonine) are available without a prescription.