What is the primary action of expectorants?

Expectorants play a crucial role in managing respiratory conditions by aiding in the clearance of mucus secretions. Their primary action is to thin and loosen mucus in the airways, making it easier to cough up and expel. This is particularly important for patients suffering from conditions such as bronchitis or asthma, where mucus can obstruct airflow and make breathing difficult. By facilitating the removal of mucus, expectorants help clear the respiratory passages, improve respiratory function, and enhance overall patient comfort.

The other options do not align with the pharmacological effects of expectorants. Inducing sleep, stimulating appetite, or lowering blood pressure pertains to different classes of medications that target other physiological processes in the body, but none of these actions are related to the function of expectorants in the respiratory system.