The purpose of this study is to investigate the exact role of Acetylcysteine (Mucomyst) in altering creatinine clearance. Prior studies have shown the protective effects of Acetylcysteine on contrast-induced renal dysfunction. In these studies, Acetylcysteine lowered the incidence of serum creatinine elevation after administration of radiographic contrast agents. Not only was the increase in serum creatinine prevented, the studies also demonstrated a significant increase in creatinine clearance after administration of the agent. These prior studies did not evaluate if the increase in creatinine clearance was indeed from a protective benefit of Acetylcysteine in preserving the GFR versus simply increasing the proximal tubular creatinine secretion without actually affecting the GFR. We propose an experiment to help support our hypothesis that Acetylcysteine increases creatinine clearance via an increase in proximal tubular secretion of creatinine.