Isotroin 20, Isotretinoin capsules are a type of medicine. It is a naturally occurring vitamin A derivative. This medication is used to treat a severe form of acne known as nodular acne, which is characterised by large, inflamed, painful acne lesions deep beneath the skin. It works on skin glands to reduce the production of sebum, a substance that can cause acne or pimples. It also has anti-inflammatory properties, which help to reduce the redness and swelling associated with acne.