Which medication use constitutes a contraindication to nitroglycerin administration?

• A. Beta blockers
• B. PDE-5 inhibitors
• C. Nitrates
• D. Aspirin

Answer: (B)

The main idea here is the dangerous interaction between nitroglycerin and PDE-5 inhibitors. Nitroglycerin works by releasing nitric oxide, which raises cGMP in smooth muscle and causes vasodilation. PDE-5 inhibitors block the breakdown of cGMP, so when both are present, cGMP levels rise much more and blood vessels dilate too much. That can lead to a dangerous drop in blood pressure, fainting, and potentially organ under-perfusion. For that reason, administering nitroglycerin while a patient has recently taken a PDE-5 inhibitor is a contraindication. Examples of these inhibitors include sildenafil, tadalafil, vardenafil, and avanafil.

Other options don’t create this specific, potentially life‑threatening interaction with nitroglycerin, though they each have their own considerations in various contexts.