2083
The bronchodilator effects of a single dose of ipratropium bromide aerosol ( 36 micrograms ) and short - acting theophylline tablets ( dose titrated to produce serum levels of 10 - 20 micrograms / mL ) were compared in a double - blind , placebo - controlled crossover study in 21 patients with stable , chronic obstructive pulmonary disease .
 ipratropium bromide, theophylline, chronic obstructive pulmonary disease
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 ipratropium bromide, theophylline, chronic obstructive pulmonary disease