The in Vitro Reduction in Viscosity of Human Tracheobronchial Secretions by Acetylcysteine.

It was recently reported that acetylcysteine (Mucomyst®) markedly reduced the viscosity of mucoprotein solutions in vitro (1). Clinical studies, in particular those by Webb (2) and Reas (3), demonstrated the usefulness of this mucolytic agent in the treatment of a variety of pulmonary disorders. In addition, Kubica and associates ( 4) found that acetylcysteine rapidly liquefied sputum for bacteriologic examination. In preparation for the clinical use of acetylcysteine, a wide variety of in vitro studies, with both human pulmonary secretion and gastric mucin mucoprotein, were conducted to evaluate factors influencing the activity of this mucolytic agent. Information was previously presented describing the action of acetylcysteine in reducing the viscosity of gastric mucin mucoprotein solutions, and showing that the mucolytic activity was due to the sulfhydryl moiety of the compound (1). The present report deals with the mucolytic action of acetylcysteine on human sputum and tracheobronchial secretions in vitro. Acetylcysteine reduces the viscosity of homogenized and unhomogenized tracheobronchial secretions to a similar degree. There· fore, although human sputum and tracheobronchial secretions exist in a gel form, most of the experiments described in this report were performed with homogenized specimens to obtain quantitative data under controlled conditions. Several of the experiments were performed with cysteine, since its mucolytic activity is similar to that of acetylcysteine. However, acetylcysteine was chosen for clinical study; for, compared to cysteine, it is more stable, does not form highly insoluble oxidation products, is less toxic, and has only slight odor