Which drug is most likely to be administered first in response to a patient experiencing severe bronchospasm following injection of iodinated contrast media?

In cases of severe bronchospasm, especially following the injection of iodinated contrast media, epinephrine is the drug of choice due to its rapid bronchodilatory effects. Epinephrine acts on both alpha and beta-adrenergic receptors, leading to vasoconstriction, increased heart rate, and, most importantly for this scenario, bronchodilation that swiftly relaxes the smooth muscles in the airways. This is critical in emergency situations where the airway is compromised, and immediate action is needed to restore normal breathing.

While other options have their uses—such as aminophylline which is a bronchodilator, or diphenhydramine (Benadryl) which is an antihistamine that could address allergic reactions—epinephrine’s rapid onset and effectiveness in treating acute bronchospasm make it the primary choice in emergency protocols. Atropine, while it can increase heart rate and reduce secretions, is not effective as a bronchodilator and is less appropriate in this scenario. Therefore, epinephrine's specific action on bronchospasm is pivotal in emergency care for patients in distress following exposure to contrast media.