Pirfisun tablet is used to treat idiopathic pulmonary fibrosis, a kind of lung illness. This condition causes scarring and stiffening of the lungs, making it difficult to breathe. It may be able to help slow the progression of your IPF. This drug should be taken as per your doctors prescription. It belongs to the pyridones class of drugs. The specific mechanism of action of pirfenidone in the treatment of idiopathic pulmonary fibrosis is unknown.