Ambroxol is used to treat certain diseases of the respiratory tract and to relieve cough associated with thickened mucous.
Guaifenesin is used to relieve cough and chest congestion.
Terbutaline is used to treat wheezing, shortness of breath, coughing, and chest tightness caused by asthma and chronic obstructive pulmonary disease (COPD; a group of lung diseases that includes chronic bronchitis and emphysema). It may also be used in premature labor.
Ambroxol belongs to a class of drugs called expectorants (aid expulsion of mucus as cough) or mucolytic (liquefy and loosen mucus). It works by liquefying and loosening thick mucus that can be coughed out easily. It helps in the production of a chemical called surfactant. Surfactant doesn't let the mucus to get stuck to the walls of airways and is easily coughed out.
Guaifenesin belongs to a class of agents called expectorants. It works by thinning the mucus in the air passages to make it easier to cough up the mucus and clear the airways.