Guaifenesin is an expectorant the action of which promotes or facilitates the removal of secretions from the respiratory tract. The precise mechanism of action of guaifenesin is not known; however, it is thought to act as an expectorant by increasing the volume and reducing the viscosity of secretions in the trachea and bronchi. In turn, this may increase the efficiency of the cough reflex and facilitate removal of the secretions. Guaifenesin is over-the-counter drug for the treatment of cough and common cold.

Guaiacol is a naturally occurring organic compound first isolated by Otto Unverdorben in 1826. Although it is biosynthesized by a variety of organisms, this yellowish aromatic oil is usually derived from guaiacum or wood creosote. Guaiacol is used as a reducing co-substrate for COX reactions. It is mainly used as expectorant, antiseptic. It is used as cough suppressant, it is an ingredient of Pulmo Bailly (UK). Pulmo Bailly Cough Expectorant is indicated for relief for cough symptoms that are associated with a flu, cold, or other infection. It contains active ingredients, Codeine and Guajacol, which reduce discomfort and the urge to cough. Each 5 ml tablespoon of Pulmo Bailly contains 75 mg guaiacol and 7 mg codeine.