Theophylline is used to treat lung diseases such as asthma and COPD (bronchitis, emphysema). It must be used regularly to prevent wheezing and shortness of breath. This medication belongs to a class of drugs known as xanthines. It works by relaxing the muscles around the airways so that they open up and you can breathe more easily. It also decreases the lungs' response to irritants. Controlling symptoms of breathing problems can decrease time lost from work or school.This medication must be used regularly to be effective. It does not work right away and should not be used to relieve sudden breathing problems. If sudden shortness of breath occurs, use your quick-relief inhaler as prescribed.