A patient reports taking sildenafil within the last 24 hours. Which medication is contraindicated?

Introduction: Sildenafil is a selective inhibitor of phosphodiesterase type 5 (PDE5), which increases cyclic guanosine monophosphate (cGMP) levels. When combined with nitrates, this synergy causes an exaggerated accumulation of cGMP, leading to profound, irreversible systemic vasodilation and a catastrophic drop in mean arterial pressure. A. Digoxin is a cardiac glycoside used for heart failure and atrial fibrillation. It has a narrow therapeutic index but does not interact with the PDE5 inhibitor pathway. There is no absolute contraindication to using digoxin in a patient who has recently ingested sildenafil for erectile dysfunction management. B. Enoxaparin is a low-molecular-weight heparin used for anticoagulation. Its mechanism involves the inhibition of factor Xa and thrombin. It does not affect vascular smooth muscle relaxation via the nitric oxide/cGMP pathway, and therefore, it does not pose a risk for acute hypotension when used with sildenafil. C. NITROGLYCERIN is strictly contraindicated within 24 to 48 hours of sildenafil use. Both drugs increase CYCLIC GMP, and their combined administration can trigger FATAL HYPOTENSION. The nurse must ensure nitrates are withheld to prevent severe coronary hypoperfusion and myocardial infarction resulting from the massive drop in systemic vascular resistance. D. Metoprolol is a cardioselective beta-1 adrenergic blocker. While it is used to manage blood pressure and heart rate, it is not contraindicated with sildenafil. While both can lower blood pressure, they do not share the synergistic biochemical pathway that makes the nitrate-sildenafil combination so uniquely dangerous to patient safety.