A 65-year-old male with coronary artery disease is prescribed Nitroglycerin. During discharge teaching, the nurse should emphasize that the patient must avoid taking phosphodiesterase type 5 (PDE-5) inhibitors, like Sildenafil (Viagra). What is the primary reason for this contraindication?

A. Increased risk of arrhythmias due to drug interactions: While both drugs affect cardiovascular function, the primary risk with concurrent use is not arrhythmias. Nitroglycerin and PDE-5 inhibitors mainly influence vascular tone, not cardiac electrical activity directly. B. Potential for life-threatening hypotension due to excessive vasodilation: Both nitroglycerin and PDE-5 inhibitors are potent vasodilators. When used together, they can cause profound hypotension due to synergistic effects on the vascular system, which may lead to syncope, myocardial infarction, or even death. C. Increased risk of severe headache due to overlapping side effects: Headache is a known side effect of both drugs due to vasodilation, but it is not the most dangerous interaction. While uncomfortable, headaches are not life-threatening compared to the risk of severe hypotension. D. Decreased effectiveness of nitroglycerin in relieving angina: There is no evidence that PDE-5 inhibitors reduce the efficacy of nitroglycerin. The concern is not about reduced therapeutic benefit but rather the risk of severe, potentially fatal cardiovascular side effects.