Many people with CF develop chronic airway infection, most importantly with Pseudomonas aeruginosa. Inhaled antibiotics deliver high drug levels straight to the lungs while limiting whole-body side effects. The two mainstays are inhaled tobramycin (TOBI and others) and aztreonam lysine (Cayston). They are often used in repeating on/off cycles (commonly 28 days on, 28 days off), sometimes alternating between the two, to suppress infection and reduce flare-ups.
Inhaled by nebulizer or dry-powder inhaler, usually in 28-day-on/28-day-off cycles, and timed after airway clearance and other inhaled medicines. The CF team selects and rotates agents based on sputum cultures and how the airways respond.
This is ongoing, cyclic maintenance therapy to suppress (not eradicate) chronic infection. Regular sputum cultures guide which antibiotic is used and when. Acute flare-ups may still need oral or IV antibiotics.