Probably worth a conversation with your doc or with your company, or both. Your doc might be able to help you with something less sedating, or to take your meds on a different schedule. There are times when working 14-15 hour shifts may just be impossible to deal with in your condition, and you have to be willing to accept your limitations if that's the case. I don't think I could consistently work those types of hours these days, even though I have in the past.