Drug-Induced

Pulmonary fibrosis (PF) is part of a larger group of more than 200 interstitial lung diseases (also known as ILDs) that are characterized by inflammation and/or scarring in the lung. In ILDs, the injury and damage occurs in the walls of the air sacs of the lung, as well as in the tissue and space around these air sacs. When an interstitial lung disease includes scar tissue in the lung, we call it pulmonary fibrosis.

Some medications can cause pulmonary fibrosis. Drugs used to treat cancer (chemotherapy drugs like bleomycin), drugs used to treat abnormal heart rhythms (such as amiodarone), drugs used to treat inflammatory conditions (such as methotrexate), and an antibiotic used to treat urinary tract infections (nitrofurantoin) are some of the better known drugs that can cause injury, inflammation, and scarring in the lungs. Numerous other drugs have been found to cause PF in some cases. It is not known why some people who use these drugs develop pulmonary fibrosis, while most do not.

When a doctor or other healthcare provider suspects that a patient has ILD, they will collect information about the patient’s medical and personal history, work and home environment, hobbies, and illness that may be present in the family (see: Diagnosis). This can help a doctor identify exposures or other diseases that might have caused lung injury and scarring. The doctor will also often order pulmonary function tests, a chest x-ray, blood work, and a high-resolution CT scan.

Pulmonary function tests measure how much air the lungs can hold, and how the lungs are working overall. Scarring can cause the lungs to shrink, and it can also make them stiff and unable to fully expand. This means the lungs are able to hold less air. Scar tissue may also affect the ability of the lungs to transfer oxygen to the bloodstream.

A high-resolution computed tomography (HRCT) scan is a special type of x-ray that shows fine detail of the lung tissue. On a CT scan (also known as CAT scan) healthy lung tissue looks nearly black, and scar tissue and inflammation appear grey or white.

Drug-induced pulmonary fibrosis can be challenging to diagnose, as the relationship between a particular drug and other underlying conditions that can affect the lungs (such as rheumatoid arthritis) can be complicated. If a medication is suspected to have caused pulmonary fibrosis, the medication history, including when it was started and stopped, dosing, and other medications taken at the same time, is a very important part of the evaluation.