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Background-Increased oxidative stress, elevated plasma homocysteine concentration, increased pulse pressure, and impaired endothelial function constitute risk factors for increased mortality in patients with end-stage renal failure. Methods and Results-We investigated the metabolic and hemodynamic effects of intravenous administration of acetylcysteine, a thiol-containing antioxidant, during a hemodialysis session in a prospective, randomized, placebocontrolled crossover study in 20 patients with end-stage renal failure. Under control conditions, a hemodialysis session reduced plasma homocysteine concentration to 58Ϯ22% predialysis (meanϮSD), whereas in the presence of acetylcysteine, the plasma homocysteine concentration was significantly more reduced to 12Ϯ7% predialysis (PϽ0.01). The reduction of plasma homocysteine concentration was significantly correlated with a reduction of pulse pressure. A 10% decrease in plasma homocysteine concentration was associated with a decrease of pulse pressure by 2.5 mm Hg. Analysis of the second derivative of photoplethysmogram waveform showed changes of arterial wave reflectance during hemodialysis in the presence of acetylcysteine, indicating improved endothelial function. Conclusions-Acetylcysteine-dependent increase of homocysteine removal during a hemodialysis session improves plasma homocysteine concentration, pulse pressure, and endothelial function in patients with end-stage renal failure.

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