Based on my experience, I took isotretinoin for more than a year, from a high dose to a smaller dose.
As per the doctor, the amount of dosage and duration required to take the meds are based on your body weight.
On top of that, your liver needs to work very well and you need to regularly have a creatinine test to ensure your kidney is working well
Before taking iso, make sure you eat something or make sure you have fatty/oily food, to maximize the effect of iso.

I stopped iso because my kidney cant take it anymore and it almost fail.

If you are required to take isotretinoin, make sure you drink lots of water and don't take it with an empty stomach. Must avoid direct sunlight, apply moisturiser and sunblock.
you may combine with topical cream - tretinoin. it works almost the same with the pill (like a chemical peel).

ps:my skin conditions still bad