A 73-year-old male patient is in the clinic for a yearly physical and is asking for a prescription for sildenafil (Viagra). He has listed on his health history that he is taking a nitrate for angina. The nurse is aware that which problem may occur if sildenafil is taken with a nitrate?

A. Reduced effectiveness of the sildenafil: Sildenafil’s effect is not the primary concern when combined with nitrates; the interaction is about additive vasodilation rather than sildenafil becoming ineffective. B. Significant decrease in blood pressure: Combining sildenafil (a PDE-5 inhibitor) with nitrates causes marked vasodilation that can produce a dangerous drop in blood pressure (severe hypotension), which is why coadministration is contraindicated. C. Significant increase in pulse rate: Although reflex tachycardia can occur with hypotension, the main clinically significant and consistently reported problem with sildenafil + nitrates is large decreases in blood pressure rather than a primary sustained pulse increase. D. Increased risk of bleeding: There is no direct mechanism by which sildenafil combined with nitrates causes increased bleeding risk; the major safety issue is hypotension.