Meclizine Hydrochloride is an antiemetic medicine for folks who suffer from
motion sickness.
One to two tablets last 24 hours, where Dimenhydrinate, marketed under the trade name Dramamine, lasts only four to six hours.
Meclizine Hydrochloride is sold under the trade name Bonine (and manufactured by Pfizer, Inc.). The normal dosage is 25 to 50 milligrams.
I've used both Dramamine and Bonine, and I find that the Bonine works much longer without the drowsiness you can get with Dramamine. I took one Bonine when I flew from San Diego, California to Bangkok, Thailand via Hong Kong, and I was able to enjoy the flight from start to finish.