I tried something different last year that really helped, no drugs needed.
I am an Occupational Therapist, I work with adults who have strokes and brain injuries and it can change your sensory system tremendously. I was talking about the motion sickness to my mom who is a school Occupational Therapist, she had just gone to a course which a 70 year old professor was teaching about Sensory Integration, the theory is you can build up your system because we only lose it and get more dizzy when we don't use it. Think about how much kids spin and move and how little we do as adults.
I started swinging a little bit at a time, til I got slightly dizzy. I have little kids remember so this fits into our playground time. I started a few months before we went. As the weeks went on I could swing longer and not get as dizzy. I am trying it again this year, I started in Jan. for our April trip.
Last year we added 4 times on SM per day and I still felt ok. The only time I needed a short recovery time was when I rode Screamin 2x with in 15 minutes.
Try it and see if it helps. It made me feel better, and I have roller coaster fanatics now that the girls are tall enough to ride all of them.