A 15-year-old boy with asthma is allergic to cats. He went to a friend's house after school who has a pet cat. Later that evening (6 hours after exposure) he stas to wheeze. Which of the following drugs should have been administered in the afternoon to prevent his symptoms?

Coicosteroids and cromolyn sodium are impoant pharmacologic agents useful in the treatment of late-phase allergic reactions, which occur 6-8 hours after exposure to an allergen. Theophylline, albuterol, and antihistamines are useful for the early or immediate allergic phase of an IgE-mediated hypersensitivity reaction, but not for the late- phase allergic response.