Pirfenidone belongs to the class of medications known antifibrotics. It is also an anti-inflammatory. Pirfenidone is used to treat adults with mild-to-moderate idiopathic pulmonary fibrosis(lung scarring), also called IPF. IPF is a condition in which the lungs become thickened, stiff or scarred over a long period of time. How pirfenidone works is not completely understood, but it may reduce inflammation and fibrosis in the lungs and may slow down the worsening of IPF.