A method for studying expectorant action in the mouse by measurement of tracheobronchial phenol red secretion.

The paper reports a method for studying mucosecretolytic drugs in the mouse. After i.p. application of phenol red, part of the dye is secreted in the tracheobronchial tract and collected by lung washings with saline. The concentration of secreted phenol red is measured photometrically at 546 nm. All the most important expectorant drugs increase the tracheobronchial secretion of phenol red in the mouse. The ED50 values, calculated as mg/kg, show practically the same activity for N-acetylcysteine, Tiopronine, SF-1284 and S-carboxymethylcysteine, and a lower activity for Ambroxol and Sobrerol. The method was validated for reproducibility utilizing Tiopronine in many experiments performed over twelve months.