I too don't like giving medical advice, especially because I'm a medical professional- that said- Please talk to your doctor and discuss your concerns and alternatives, there are many very effective anti-nausea medications that can be prescribed to you before you leave for your cruise.
As for Bonine (meclazine): When prescribed by your doctor it's prescribed as a 12.5mg tablet. How the dosage to be taken is written varies. Bonine OTC is a 25mg chewable tab. When I take it, I break it in half to make it 12.5mg. I feel that if the smaller dose works, all the better.
If you aren't sure motion sickness is a problem for you, your doctor may advise you to take a dose about an hour before you board the ship.
Compazine, available by prescription only, is a very effective anti-emetic. Antivert, Tigan and Reglan are also possibilities that your doctor may consider. Without getting too technical, these drugs work the same way antihistamines do - so drowsiness is always a possibility depending on how your particular system reacts to them. I've never had drowsy side effects that bothered me from any of them. Drinking is not advised while taking any of the medications mentioned, as it can exacerbate the side effects. The Scopolomine patch is another option, but the side effects can leave you feeling very drowsy. I saw my husband sleep so soundly he was drooling after putting one on before a fishing trip once. <G> Everyone reacts differently.
Sea-Bands have been known to work very well for some people. Ginger tablets, ginger tea and even ginger-ale are all reported to be soothing on the stomach.
I always give my doctor a call pre-cruise and ask his advice. I tell everyone who asks me to do the same. My feeling is - better safe than sorry. Once motion sickness progresses to vomiting, it's often hard to stop without medical intervention. (an injection of Compazine and Phenergan works miraculously). So, I'd say prevention is key.
If you start to feel ill, take something and get yourself outside. (Your balcony if you have one or an upper deck) Fresh air and focusing on the horizon helps to quell the confusion in the brain which is what starts the process to begin with. Limit your food and liquid intake until you are feeling better. Usually, your brain and middle ear adjust by the second or third day and if seas are calm you may not even notice anything and have no problems at all.
I hope I didn't confuse you. Again, a quick call to your doctor before you leave will set you at ease, and he may prescribe something for you to bring with you that he feels suits your needs best. Prevention is key. (did I say that enough times? lol- sorry)
Have a Great Cruise,