An 81-year-old man with stable coronary artery disease, hype…

An 81-yeаr-оld mаn with stаble cоrоnary artery disease, hypertension, and type 2 diabetes asks the gerontology clinic nurse about starting sildenafil (Viagra) for erectile dysfunction. He takes aspirin 81 mg, metoprolol 50 mg BID, lisinopril 20 mg, and atorvastatin.Which teaching point by the nurse is most important for safety?