A 65-year-old male presents with concerns about erectile dysfunction. He has a history of prior heart attack, high blood pressure, diabetes, hyperlipidemia, benign prostatic hyperplasia, and stroke. He currently takes metoprolol, aspirin, metformin, insulin, simvastatin, amlodipine, lisinopril, and tamsulosin. Which of the following medication combinations could cause a serious adverse effect of concurrently prescribed?