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The respiratory system is responsible for mediating gas exchange between the external environment and the bloodstream. The upper respiratory tract conducts air to the lower respiratory passages and ultimately to the lungs. It also humidifies and conditions inspired air and serves to protect the lungs from harmful substances. In the lungs, gas exchange takes place between the alveoli and the pulmonary circulation.

The drugs discussed in this chapter are directed primarily at maintaining proper airflow through the respiratory passages. Agents that treat specific problems in the lungs are not discussed here but are covered in other areas of this text. For instance, Section 8 (Chapters 33 to 35) includes drugs used to treat infectious diseases of the lower respiratory tract and lungs.

The respiratory agents presented here are divided into two primary categories. The first group includes drugs that treat acute and relatively minor problems, such as nasal congestion, coughing, or a seasonal allergy. The second category includes drugs that treat more chronic and serious airway obstructions, such as bronchial asthma, chronic bronchitis, and emphysema.

You will frequently treat patients with both acute and chronic respiratory conditions. Drug therapy can be critical in helping these patients breathe more easily and become more actively engaged in respiratory muscle training and various forms of aerobic and strengthening exercises. Patients will also be calmer and more engaged in rehabilitation activities if these medications improve difficult and labored breathing and reduce the anxiety and panicky sensation that occurs when patients feel they “cannot get enough air.” Consequently, the overview of the drugs presented in this chapter is of interest.


The drugs presented below are used to treat symptomatic coughing and irritation resulting from problems such as the common cold, seasonal allergies, and upper respiratory tract infections. Many of these drugs are found in over-the-counter preparations. Often, several different agents are combined in the same commercial preparation; for example, a decongestant, an antitussive, and an expectorant may be combined and identified by a specific trade name. Also, agents within a specific category may have properties that overlap into other drug categories. Certain antihistamines, for instance, may also have antitussive properties.


Antitussive drugs suppress coughing associated with the common cold and other minor throat irritations. When used to treat cold and flu symptoms, these drugs are often combined with aspirin or acetaminophen and other respiratory tract agents.1,2 Antitussives are typically recommended for short-term use in relieving symptomatic coughing.3 Nonetheless, the extensive use of antitussives has been questioned in our society. Coughing is a type of defense mechanism that can help expel mucus and foreign material from the upper respiratory tract.4 By inhibiting this mechanism, antitussives may reduce the ability of coughing to ...

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