18.6: Upper Respiratory Drugs: Antitussives, Expectorants, and Mucolytics

Respiratory symptoms, such as congestion and cough, commonly accompany respiratory tract conditions. Various medications, such as antitussives, expectorants, and mucolytics, play crucial roles in providing relief.

Antitussives include codeine, dextromethorphan (Robitussin), and benzonatate (Tessalon). Codeine and dextromethorphan exert their effects centrally by suppressing the cough reflex center in the medulla. Benzonatate operates peripherally within the respiratory tract by anesthetizing stretch receptors in the respiratory passages. Antitussives reduce dry coughs that do not produce mucus (nonproductive coughs), offering relief from persistent bouts of coughing.

Expectorants, such as guaifenesin (Mucinex), adopt a different strategy. While their exact mechanism is not fully understood, they are believed to reduce the viscosity of mucus, making it easier to expel, but they do not necessarily increase the production of respiratory secretions. This reduction in viscosity eases the expulsion of mucus from the respiratory passages (productive coughs), proving particularly beneficial in cases marked by thick, adhesive mucus.

Mucolytics, another facet of respiratory care, use a different mechanism. Agents like acetylcysteine (Mucomyst) and dornase alfa (Pulmozyme) break down the molecular structure of thick mucus concentrated in the lower sections of the lungs. As a result, the elimination of this stubborn mucus becomes notably easier. Acetylcysteine, for instance, is used to treat conditions like pneumonia, bronchitis, and cystic fibrosis, where thick mucus poses a significant hindrance.

These medications are not without their potential drawbacks. With antitussives especially, side effects such as lightheadedness, dizziness, and drowsiness may arise, particularly when combined with other CNS depressants, including antihistamines. Antitussives and expectorants also warrant special caution during pregnancy, lactation, and for patients with asthma.

Antitussives can cross the placental barrier and potentially affect the developing fetus. While research on the direct risks of antitussives in pregnancy is limited, healthcare providers should be cautious to avoid unnecessary medication exposure to the fetus. Although expectorants are generally considered safer than antitussives during pregnancy, there is still limited research on their effects on fetal development. Pregnant women are often advised to consult their healthcare provider before using expectorants to ensure that potential benefits outweigh potential risks.

For patients with asthma, suppressing coughs can be problematic because coughing serves as a defense mechanism to clear mucus and irritants from the airways. If mucus accumulates in the airways due to suppressed coughing, it can exacerbate asthma symptoms and potentially trigger an asthma attack. Mucolytics can lead to increased congestion and potentially worsen asthma symptoms, and should be used with care.

Common respiratory discomforts, including congestion and cough, can be relieved using antitussives, expectorants, and mucolytics.

Antitussives, like codeine and dextromethorphan, act centrally and suppress the cough reflex center in the medulla. In contrast, benzonatate acts peripherally on the respiratory tract. Antitussives alleviate nonproductive coughs, providing relief from persistent coughs.

Expectorants, like guaifenesin, enhance respiratory secretion production, reducing mucus viscosity.

This facilitates mucus expulsion from the respiratory passages, aiding conditions characterized by thick, sticky mucus.

Mucolytics, such as acetylcysteine and dornase alfa, break down thick mucus in the lower portions of the lungs, easing elimination.

Acetylcysteine is used to treat pneumonia, bronchitis, and cystic fibrosis.

This drug poses potential side effects, including lightheadedness, dizziness, and drowsiness, especially when combined with an antihistamine.

Antitussives and expectorants warrant caution during pregnancy, lactation, and in asthma patients.

Mucolytics, in general, are not recommended for asthma patients.