I agree and disagree.
You have a point about the cleanse. It would be trading toxins, for fresh toxins.
Why not wait until after your Accutane prescription is completed. And then attempt a cleanse. That sounds the most beneficial to me.
In that way, you'll have the clear skin from Accutane, and can do a cleanse which will help your skin stay clearer, longer.
And #60824 during mine, and two of my close friends time on Accutane the worst side effect we experienced was dry skin.
If your too afraid to take a risk, you'll finish on top. The same rule applys with Acne.