I've always wondered about that, too. I've often read to carry a copy of the written prescription, along with having the medicine in its original, labeled container. Well, you can't carry the written prescription, the pharmacy keeps that!
I've never had my medicines questioned, but we went to Russia several years ago and I was somewhat concerned, especially since some of the medicines I had were controlled substances. The pharmacist made copies for me. The pharmacy was in a grocery store with a bank and a notary, so we had the letter from the pharmacist notarized. That is, he copied the prescriptions, then wrote a note to the effect that this was a true and original copy of the prescription on file, then the whole letter was notarized. We didn't need it, but it made me feel better. You can't make copies of your own prescriptions, they have a watermark which will show up "illegal copy". Try showing that to Russian custom officials!

Well, that only works if you can use a local pharmacy. We have to use a mail order pharmacy right now, and we're lucky just to get the medicines, let alone the 8 x 10 color glossys with words of explanation written on the back!
There's just so many new security regulations right now its hard to know what to do. All the security regulations are quite necessary, but confusing to deal with. My husband said the other day that maybe we should just all fly naked wit no carry ons to speed up the security process!
