Final Answer:
The patient that has been prescribed sildenafil (Viagra) for erectile dysfunction should avoid taking nitroglycerin with this drug. Therefore, the correct option is C. Avoid taking nitroglycerin with this drug.
Step-by-step explanation:
Sildenafil, commonly known as Viagra, is a phosphodiesterase type 5 (PDE5) inhibitor primarily used for erectile dysfunction. Option C, "Avoid taking nitroglycerin with this drug," is the correct instruction. Both sildenafil and nitroglycerin cause vasodilation, and when taken together, they can lead to a dangerous drop in blood pressure. This is particularly critical for patients with a history of cardiovascular issues. It is crucial to emphasize the importance of informing healthcare providers about any nitrate medications to avoid potential life-threatening complications.