Most people who have COPD are on more than one medication to control their disease. EFFORTS has published a chart of which medications should not be taken together.
http://copd.about.com/od/copd/fl/Dont-combine-these-COPD-medicines.htm?utm_content=20160124&utm_medium=email&utm_source=exp_nl&utm_campaign=list_copd&utm_term=list_copd