The nurse is caring for a patient in the ED who has edema of the tongue and lips. He has been taking all of his prescribed drugs at home prior to coming to the hospital. Which one is most likely responsible for the adverse effects he is experiencing at this time?

Introduction: Angioedema is a potentially life-threatening adverse reaction characterized by rapid subcutaneous or submucosal swelling. When associated with ACE inhibitors, it results from the inhibition of kininase II, leading to an accumulation of bradykinin, which increases vascular permeability in the upper airway and facial structures. A. Isosorbide dinitrate is an organic nitrate used primarily for the management of angina pectoris. Its primary side effects are related to systemic vasodilation, such as orthostatic hypotension, syncope, and severe pulsating headaches. It is not associated with the bradykinin-mediated pathways that trigger the edema of the tongue and lips. B. LISINOPRIL, an Angiotensin-Converting Enzyme (ACE) inhibitor, is the most likely culprit for ANGIOEDEMA. By blocking the breakdown of BRADYKININ, it causes profound local vasodilation and fluid extravasation. This reaction can occur at any time during therapy and requires immediate cessation of the drug to prevent total airway obstruction. C. Amlodipine is a dihydropyridine calcium channel blocker. While it frequently causes peripheral edema, typically localized to the lower extremities (ankles and feet) due to precapillary vasodilation, it does not typically cause the acute, localized swelling of the tongue, lips, or oropharynx seen in ACE inhibitor-induced reactions. D. Clonidine is a centrally acting alpha-2 adrenergic agonist used for hypertension. Its common side effect profile includes xerostomia (dry mouth), sedation, bradycardia, and rebound hypertension if discontinued abruptly. It does not possess a pharmacological mechanism that would result in the sudden development of facial or mucosal angioedema.