Safety and Efficacy of Sildenafil in Cystic Fibrosis (CF) Lung Disease

This study is an open-label study that examines the use of sildenafil (Revatio) in clinically stable patients with mild to moderate CF lung disease. The length of participation for each subject will be approximately 10 weeks, and will consist of a screening visit, a study visit for initiation of study drug if subject qualifies, interim visits to escalate drug dose, obtain drug levels, review concomitant medications and assess side effects, a visit at the end of the therapy period (to reassess inflammatory markers, laboratory studies and side effects,) and a follow-up assessment 2 weeks after subject completion.