Accutane (Isotretinoin) is a form of vitamin A. I would imagine that an Accutane overdose would be akin to a vitamin A overdose - unpleasant, slow, and expensive (cost me ~$100 CAD/month).
Here's symptoms of an overdose:
I am by no means an expert but I did personally do a round of Accutane for my acne. Even getting Accutane is hard in my experience. If you go to the doctor for mild-moderate acne they usually give you a topical like Retin-A, benzoyl peroxide, etc. If that doesn't work, antibiotics are usually prescribed. Accutane is typically reserved for severe acne or treatment resistant acne. To get it, you have to get a blood test, then sign a wavier, and get monthly blood tests/doctor's visits when you're on it. If you're female you have to go on birth control too as it causes birth defects. In the wavier it is noted that Accutane itself has been linked to an increased risk of depression + suicide.
Overall I wouldn't recommend trying this to CTB. I still remember how I felt on Accutane - like complete shit lol. I haven't broken out in like 6/7 years though :)
