Cystic fibrosis is a condition in which thick mucus is formed in the lungs and breathing passages.
The mucus blocks the airways and increases the chance of lung infections. The infections then cause the mucus to become even thicker, making it more difficult to breathe. Dornase alfa will not cure cystic fibrosis. However, when it is used every day, it helps make breathing easier and reduces the number of serious lung infections that require treatment with antibiotics. In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do.