The Food and Drug Administration on Monday approved a Forest Laboratories drug for long-term treatment of the deadliest form of lung disease.

Tudorza Pressair is an inhalable powder designed to improve breathing in patients with chronic obstructive pulmonary disease. Patients with the disease experience narrowing of the airways to the lungs, which can cause chronic coughing and excessive phlegm. Forest’s twice-a-day drug relaxes the lung airways to improve airflow.

Cigarette smoking is the leading cause of chronic obstructive pulmonary disease, which is the fourth leading cause of death in the U.S., according to the FDA.

Tudorza Pressair can cause serious side effects, including pressure on the eyes and urinary retention. More common side effects include headache, inflammation and cough.

The drug is not recommended for patients younger than 18.

Shares of New York-based Forest Laboratories Inc. fell 62 cents to close at $34.28.