Yes, but if the bottle has a picture of a donkey on it you may be required to bray several times to various customs officials. ha I am in one of those moods man, no idea, but good question, doubt it would work with vet stuff and you would have to bring back only the ester you had a script for so considering the human shit is so expensive over there it most likely would not be worth it.
I wondered the same about having a script for test and getting envelopes of like 10 grams of test powder in each. What can they say? They can't get you on possession if you had a script so worse case you lose the $15 the powder cost you. Repeat this several hundred times and buy a few gallons of Wesson and you should be good for several lifetimes. Seems to work quite well without the script but having one would be nice too.