My dermatoligist said the "cumulative dose" (how long and how much total into your body) is whats important when you do accutane, he's got me on for 6 months. 2 at 40mg ed, 2 at 60mg ed, 2 at 80mg ed. even though I'm completely clear now we're running the whole 6 months so that i wont need a second course.
I was just about completely cleared up after the second month at 40mg...
the medication is pricey though, do what i did...
www.ehealthinsurance.com get yourself a PPO plan (probably a lil over 100 a month) if you dont have health insurance (an HMO won't cut it)
then go to as many derms in the list as it takes until you find someone comfortable to prescribe it to you, your insurance should cover the majority of it ($15 for generic prescription for me)
there might be a few extra bucks you have to pay (whats not covered in your bloodwork) but it all works out well and you save money