Cystic fibrosis (CF) is a lethal genetic condition that affects 30,000 children and adults in the United States. Although CF management has improved substantially over the past two decades, there is still no cure and most patients with CF die before reaching their 50th birthday, largely due to lung failure. There is growing evidence that excess lung and blood inflammation that occurs in response to infections in the lungs cause CF patients to be sicker. Simvastatin is a drug that is used to lower cholesterol, but many researchers have found that this drug may also treat blood and lung inflammation. In this study, we will determine whether or not simvastatin can treat blood and lung inflammation in patients with CF and most importantly determine whether or not it can make these patients feel better and have better lung function.