The purpose of this study is to determine how two medications, azithromycin and inhaled tobramycin, work when taken together to treat cystic fibrosis (CF) patients with chronic pseudomonas aeruginosa (PA) lung infections. Some data suggest that azithromycin and inhaled tobramycin do not work well when used together. Our researchers want to determine if taking azithromycin with inhaled tobramycin has a negative impact on how well people with CF breathe. They also want to determine if the combination of medications improves or worsens the health of people with CF.
Azithromycin is approved by the Food and Drug Administration (FDA) for treatment of certain types of infections, such as ear infections, and some types of pneumonia in adults and children older than 6 months of age. Since the FDA has not approved azithromycin for treatment of CF, it is considered an investigational drug in this study. Inhaled tobramycin, an antibiotic, is inhaled as either a solution or dry powder. The FDA has approved it for CF patients age 6 and older with a PA infection. Some study participants will receive a placebo (an inactive substance) instead of azithromycin.