An in vitro comparison of the mucoactive properties of guaifenesin, iodinated glycerol, surfactant, and albuterol

Study objective: The mechanism of action of potential mucoactive agents cou ld relate to effects on the mucociliary apparatus or to direct effects on t he secretions. The purpose of this study was to determine the in vitro effe cts of several agents on the properties of mucus simulants and sputum colle cted from 30 adults with stable chronic bronchitis. Design: Sputum or simulants were analyzed untreated and after the addition of the test agent at 1:5 volume to volume ratio for a contact period of 60 s. The concentrations of the agents were as follows: guaifenesin, 20 mg/mL; iodinated glycerol, 3 mg/mL; surfactant (Exosurf; Glare Wellcome; Research Triangle Park, NC) containing 13.3 mg of phospholipid per milliliter; albu terol, 5 mg/mL; and amphibian Ringer's solution (ARS) as a control. Dynamic viscoelasticity and surface mechanical impedance were measured in a magnet ic microrheometer. Cohesiveness was measured using a filancemeter. The wett ability of a hydrophilic surface was measured using an image processing sys tem. The mucociliary transportability of sputum was timed on the frog palat e, and cough transportability (CTR) was measured in a cough machine. Results: When compared to sputum that had no test agent or ARS added, all a gents reduced sputum elasticity G', with surfactant, albuterol, and guaifen esin significant at p < 0.001. As well, guaifenesin (p = 0.006), albuterol (p = 0.003), and surfactant (p = 0.02) decreased surface mechanical impedan ce (frictional adhesiveness) compared to untreated sputum. However, there w ere no significant changes in wettability, hydration, cohesiveness, or CTR with any agent, and there were no significant changes in the propel-ties of sputum or simulants treated with test agents when compared to those treate d with ARS. Guaifenesin irreversibly disrupted mucociliary transport when a pplied directly to the frog palate. Conclusions: These agents appear to have a minimal direct action on sputum in vitro, suggesting that at the concentrations studied, these agents do no t have a significant beneficial effect on either the mucociliary transporta bility or CTR of chronic bronchitis sputum. However, there could be an effe ct of some of these agents after oral administration, especially if there i s a secondary effect of the agent on an effector cell.