Antitussive drugs suppress or inhibit coughing.
Antitussives are typically used to treat dry,
nonproductive coughs. The major antitussives include:
Antitussives are absorbed well through the GI
tract, metabolized in the liver, and excreted in urine.
Antitussives act in slightly different ways.
Benzonatate acts by anesthetizing stretch receptors
throughout the bronchi, alveoli, and pleurae.
Codeine, dextromethorphan, and hydrocodone suppress
the cough reflex by direct action on the cough center in the medulla of the
brain, thus lowering the cough threshold.
The uses of these drugs vary slightly, but each
treats a serious, nonproductive cough that interferes with a patient’s ability
to rest or carry out activities of daily living.
Benzonatate relieves cough caused by pneumonia,
bronchitis, the common cold, and chronic pulmonary diseases such as emphyse-ma.
It can also be used during bronchial diagnostic tests, such as bronchoscopy,
when the patient must avoid coughing.
Dextromethorphan is the most widely used cough suppressant in the United
States and may provide better antitussive effects than codeine. Its popularity
may stem from the fact that it isn’t associated with sedation, respiratory
depression, or addiction at usual doses.
The opioid antitussives (typically codeine and
hydrocodone) are reserved for treating an intractable cough.
Antitussives may interact with other drugs.
§ Codeine and hydrocodone may cause excitation,
an extremely elevated temperature, hypertension or hypotension, and coma when
taken with monoamine oxidase inhibitors (MAOIs).
§ Dextromethorphan use with MAOIs may produce
excitation, an elevated body temperature, hypotension, and coma.
§ Codeine taken with other central nervous
system (CNS) depres-sants, including alcohol, barbiturates, phenothiazines, and
seda-tive-hypnotics, may increase CNS depression, resulting in drowsi-ness,
lethargy, stupor, respiratory depression, coma, and even death. (See Adverse reactions to antitussives.)