In cystic fibrosis, the patient’s lungs produce too much thick mucus, which allows bacteria to grow more easily. In patients with cystic fibrosis, P. aeruginosa infections usually start in the first 10 years of life and can cause long-term lung problems.

The active substance in Cayston, aztreonam, is an antibiotic that belongs to the group ‘beta-lactams’. It works by attaching to proteins on the surface of the P. aeruginosa bacteria. This prevents the bacteria from building their cell walls, which kills them.

Aztreonam has been available as an injection since the 1980s as an ‘arginine salt’. In Cayston, aztreonam is available as a ‘lysine salt’, which makes it possible for the antibiotic to be breathed directly into the lungs without causing irritation.