Im also taking Accutane, and i think you should avoid Vitamin A altogether. Your basically overdozing yourself with vitamin A when taking Accutane. And adding more to your system is not a good idea. My doctor have treated over 1000 Accutane patients, and he strongly said to not take any vitamin A vitamins, even if its from a multi-vitamin supplements like you said. Just check other peoples journals, or better yet go to an Accutane message board and you'see what im talking about.
Good luck with the treatment