Which drug is classified as a mast cell stabilizer?

Mast cell stabilizers are a class of medications that work by inhibiting the release of inflammatory mediators from mast cells, which helps to prevent allergic symptoms and asthma attacks. Cromolyn is the primary example of this type of drug. It prevents mast cells from releasing histamine and other substances that trigger inflammation and allergic responses, making it effective for the prevention of asthma symptoms and allergic reactions.

In contrast, other options listed serve different purposes. Theophylline is a bronchodilator that relaxes the muscles of the airways to improve airflow, while Ipratropium is an anticholinergic medication used primarily for its bronchodilatory effects. Montelukast is a leukotriene receptor antagonist that helps to reduce inflammation and improve breathing in individuals with asthma and allergic rhinitis, but it does so through a different mechanism than mast cell stabilization. Thus, Cromolyn stands out as the correct answer, being specifically designed to stabilize mast cells and prevent the release of pro-inflammatory agents.