I have 4 medical diseases that cause the need for me to have about 10 different prescriptions.
I always use a pill box/reminder but I always get a letter from my dr listing the prescriptions, doses and instructions of each.
I make a few copies, keep original with me, leave one in my carry on and one in my actual luggage. (No idea why I do that).
I have traveled across country, outside the mainland US and been on 3 cruises. I have yet to have any issues.