Pirfenidone is a medication used in the treatment of idiopathic pulmonary fibrosis (IPF), a progressive and potentially fatal lung disease characterized by scarring (fibrosis) of the lungs. It belongs to a class of drugs known as antifibrotic agents.

The exact mechanism of action of pirfenidone in treating IPF is not fully understood, but it is believed to inhibit the production of certain proteins involved in the formation of scar tissue in the lungs. By reducing the buildup of scar tissue, pirfenidone helps to slow down the progression of IPF and preserve lung function.