The correct answer is F. As is common for many older patients, this man is taking several prescription medications. Though a couple of his prescriptions should be used with caution with sildenafil (captopril and propranolol), the only one that might significantly interact with sildenafil is sublingual nitroglycerin. Nitroglyc- erin is used for prompt relief of an ongoing at- tack of angina precipitated by exercise or emo- tional stress. Nitrates relax vascular smooth muscle by their intracellular conversion to nitrite ions and then to nitric oxide, which in turn activates cGMP and increases the cell’s cGMP level. Elevated cGMP ultimately causes vascular smooth muscle relaxation. This is the same mechanism sildenafil uses to cause smooth muscle relaxation and increased blood flow into the corpus cavernosum at a certain level of sexual stimulation. Using these drugs together can lead to severe hypotension and cardiovascular collapse.
Answer A is incorrect. Aspirin and sildenafil have no known dangerous interactions.
Answer B is incorrect. Captopril and sildenafil have no known dangerous interactions, though the combination may increase the risk of hypotension-related adverse effects. However, the captopril is probably contributing to his erec- tile dysfunction.
Answer C is incorrect. Fluoxetine and silden- afil have no known dangerous interactions. However, the fluoxetine is probably contribut- ing to his erectile dysfunction.
Answer D is incorrect. Lovastatin and silden- afil have no known dangerous interactions.
Answer E is incorrect. Metformin and silden- afil have no known dangerous interactions.
Answer G is incorrect. Propranolol and sildenafil have no known dangerous interac- tions, though the combination may increase the risk of hypotension related adverse effects. However, the propranolol may be contributing to his erectile dysfunction.