Beginning 1 hour before departure, susceptible people may be given nonprescription dimenhydrinate, diphenhydramine, meclizine, or cyclizine in the following doses: Dimenhydrinate: Adults and children > 12 years, 50 to 100 mg orally every 4 to 6 hours (not to exceed 400 mg / day); children 6 to 12 years, 25 to 50 mg orally every 6 to 8 hours (not to exceed 150 mg / day); children 2 to 5 years, 12.5 to 25 mg orally every 6 to 8 hours (not to exceed 75 mg / day) Diphenhydramine: Adults, 25 to 50 mg orally every 4 to 8 hours; children ≥ 12 years, 25 to 50 mg orally every 4 to 6 hours; children 6 to 11 years, 12.5 to 25 mg orally every 4 to 6 hours; children 2 to 5 years, 6.25 mg orally every 4 to 6 hours Meclizine: Adults and children ≥ 12 years, 25 to 50 mg orally every 24 hours Cyclizine: Adults, 50 mg orally every 4 to 6 hours; children 6 to 12 years, 25 mg 3 or 4 times a day Cyclizine and dimenhydrinate can minimize vagally mediated gastrointestinal symptoms.