Both Dramamine and Bonine can cause drowsiness, although this side effect is reported at a higher prevalence with the Dramamine (~20-25% versus ~6% for Bonine). Dramamine belongs to the antihistamine class of drugs, and is not related Ativan (an antidepressant/anti-anxiety drug in the same class as Valium).
Hope this is the information that you need! Happy cruising!
John Burns, R.Ph.