It's probably an individual thing. My son was on 40mg but due to it worsening the Dermatologist suggested 40mg every second day and anti-biotics to reduce the possibility of scaring....so that may be worth keeping in mind.
I don't usually enter posts like this but I'll make an exception here for the information of other parents of kids going through bad acne. I, like my son started getting bad acne around 13. Accutane (Roaccutane in Aust.) wasn't around when I was a teen & I only found out about it when I was in my early 30's. Roaccutane had only just come out when I started so there wasn't a whole lot of negative press out there... nor was the internet. As for myself, I can't remember having any bad side ef