Which antianginal medication is of particular concern for a patient using a PDE-5 inhibitor?

Nitroglycerin is the correct answer because it is a nitrate that works as a potent vasodilator. When used in combination with phosphodiesterase type 5 (PDE-5) inhibitors, such as sildenafil (Viagra), there is a significant risk of severe hypotension. PDE-5 inhibitors enhance the effect of nitric oxide by preventing its breakdown, which also increases levels of cyclic guanosine monophosphate (cGMP). Nitroglycerin further elevates cGMP, leading to excessive vasodilation. This combination can result in profound hypotensive crises, which can be life-threatening.

In contrast, the other antianginals listed do not pose the same level of risk. Metoprolol is a beta-blocker that manages heart rate and myocardial oxygen demand but does not interact dangerously with PDE-5 inhibitors. Diltiazem, a calcium channel blocker, also does not have the same vasodilatory effects in combination with PDE-5 inhibitors as nitroglycerin does. Amlodipine, another calcium channel blocker, similarly lacks the risk for severe hypotension when combined with PDE-5 inhibitors. Thus, the concerns surrounding the use of nitroglycerin with PDE-5 inhibitors highlight