Tretiva 20 And Isotroin 20 mg is a brand name for Isotretinoin, a medication primarily used to treat severe acne, particularly cystic or nodular acne that hasn’t responded to other treatments. Isotretinoin is a powerful retinoid, which means it’s related to vitamin A and works by reducing the amount of oil released by oil glands in your skin, helping your skin renew itself more quickly.