Upper respiratory infections are among the most com- mon afflictions of humans. The drugs used to treat the discomfort associated with an upper respiratory infection include antitussives, mucolytics, and expectorants.Many of these drugs are available as nonprescription (over-the-counter) drugs, whereas others are available only by prescription.
Coughing is the forceful expulsion of air from the lungs. A cough may be productive or nonproductive.With a productive cough, secretions from the lower respiratory tract are expelled. A nonproductive cough is a dry, hacking one that produces no secretions. An antitussive is a drug used to relieve coughing. Many antitussive drugs are combined with another drug, such as an antihistamine or expectorant, and sold as nonprescription cough medicine. Other antitussives, either alone or in combination with other drugs, are available by prescription only.
ACTIONS of Antitussives
Some antitussives depress the cough center located in the medulla and are called centrally acting drugs. Codeine and dextromethorphan are examples of centrally acting antitussives. Other antitussives are peripherally acting drugs,which act by anesthetizing stretch receptors in the respira-tory passages, thereby decreasing coughing. An example of a peripherally acting antitussive is benzonatate (Tessalon).
USES of Antitussives
Antitussives are used to relieve a nonproductive cough.When the cough is productive of sputum, it should betreated by the primary health care provider who, based on a physical examination, may or may not prescribe or recommend an antitussive.
ADVERSE REACTIONS of Antitussives
Use of codeine may result in respiratory depression,euphoria, light-headedness, sedation, nausea, vomiting,and hypersensitivity reactions. The more common adverse reactions associated with the antitussives When used as directed, nonpre-scription cough medicines containing two or more ingre-dients have few adverse reactions. However, those that contain an antihistamine may cause drowsiness.
CONTRAINDICATIONS of Antitussives
Antitussives are contraindicated in patients with known hypersensitivity to the drugs. The narcotic anti-tussives (those with codeine) are
contraindicated in premature infants or during labor when delivery of a pre-mature infant is anticipated. Codeine is a Pregnancy Category C drug except in the pregnant woman at term or when taken for extended periods, when it is consid-ered a Pregnancy Category D drug.
All antitussives are given with caution to patients with a persistent or chronic cough or when the cough is accompanied by excessive secretion. Individuals with a high fever, rash, persistent headache, nausea, or vomit-ing should take antitussives only when advised to do so by the primary health care provider. Antitussives con-taining codeine are used with caution in patients having an acute asthmatic attack, those with COPD, and those with pre-existing respiratory disorders. Administration of codeine may obscure the diagnosis in patients with acute abdominal conditions.
Antitussives containing codeine are classified as Pregnancy Category C (during pregnancy) and Pregnancy Category D (during labor) drugs. Safe use of non-narcotic antitussives during pregnancy has not been established. They are used with caution and only when clearly needed during pregnancy and lactation.
The narcotic antitussives are used cautiously in patients with head injury and increased intracranial pressure, acute abdominal disorders, convulsive disorders, hepatic or renal impairment, prostatic hypertrophy, and asthma or other respiratory conditions.
Other central nervous system (CNS) depressants and alcohol may cause additive depressant effects when administered with antitussives containing codeine.
When dextromethorphan is administered with the monoamine oxidase inhibitors patients may experience hypotension, fever, nausea, jerking motions to the leg, and coma.