Treatment of Aspergillus Fumigatus (a Fungal Infection) in Patients With Cystic Fibrosis

Inclusion Criteria * Diagnosis of CF as defined by two or more clinical features of CF and a documented sweat chloride greater than 60 mEq/L by quantitative pilocarpine iontophoresis test or a genotype showing two well characterized disease causing mutations * Patient must be known to be chronically colonized with Aspergillus fumigatus. * Patients must be clinically stable at randomization, no use of new inhaled, oral or intravenous antibiotics or oral or intravenous corticosteroids during the 14-day period prior to randomization. * 6 years of age and older * Patients must weigh at least 20 kg * Post-menarche females must be using an effective form of contraception. Exclusion Criteria * Inability to give informed consent. * Respiratory culture positive for B.cepacia complex * Renal function abnormalities-Creatinine greater than 1.5 times upper limit of normal within a 30 day period prior to randomization * Liver function abnormalities : AST or ALT greater or equal to 2.5 times the upper limit of normal within a 30 day period prior to randomization * Neutropenia, absolute neutrophil count\< or = 1000 within a 3-day period prior to randomization * History of biliary cirrhosis documented by liver biopsy or imaging. * History of portal hypertension. * Investigational drug use within 30 days of randomization date. * History of alcohol, illicit drug or medication abuse within 1 year of randomization. * Women who are pregnant, breastfeeding or trying to conceive