My daughter had a prescription for this a few years ago from a family practice doctor. We ended up changing doctors and not using it so I don't have personal experience with it. That doctor told me that his patients (mostly adults) either loved it or it did nothing for them. He said he prescribed it for people and their friends would come in and ask for it. He said we should try it and if there was no benefit to just stop it. I can't remember exactly how long he said to try it, but I think it was less than a month because I remember him saying if it didn't work for her, I could take it. He made it seem like it was magic candy he was handing out LOL.
Since it seemed new at the time and with his casual attitude, I was trying to find out more about it before giving it to her. I did end up deciding it would be ok but, for other reasons, we switched doctors. The next doctor had a different plan.