Chronic obstructive pulmonary disease (COPD) is a long-term lung disease that is caused by cigarette smoking or by breathing in other lung irritants, including pollution, dust, or chemicals. The purpose of this study is to evaluate the effectiveness of zileuton, a medication that is used to control asthma symptoms, at reducing the length of a hospital stay for adults who are hospitalized for a COPD exacerbation, or worsening of COPD symptoms.