I was recommended to use isotretinoin 40 mg capsules but however doctor told me that I can lower the dosage if side effects are pretty high and the only thing is it could increase the duration of treatment. But however due to the heavy dryness I proffered using 20 mg. Its been 3 months and I am on isotretinoin. For the first month I took 30 mg daily. Second month 20 mg daily .third month 10 mg. How long I need to use them?