Which of the following medications is NOT an inhaled corticosteroid?

Montelukast is not an inhaled corticosteroid because it belongs to a different class of medications known as leukotriene receptor antagonists. While inhaled corticosteroids, like Budesonide, Fluticasone, and Beclomethasone, work by reducing inflammation directly in the airways, montelukast operates by blocking the action of leukotrienes, substances in the body that contribute to inflammation, bronchoconstriction, and mucus production in asthma and allergic rhinitis. Thus, while both types of medications are used in managing respiratory conditions, they have distinct mechanisms of action and belong to separate drug classes. This fundamental difference is what makes montelukast the correct answer, as it does not fall under the category of inhaled corticosteroids.