By increasing sputum volume and making sputum less viscous, guaifenesin facilitates expectoration of retained secretions.
Codeine is a centrally acting antitussive agent.
Dextromethorphan is a synthetic nonopioid cough suppressant, the dextro isomer of the codeine analogue of levorphanol. Dextromethorphan acts centrally to elevate the threshold for coughing but does not have addictive, analgesic or sedative actions and does not produce respiratory depression with usual doses.