A 65-year-old male with a history of hypertension and benign prostatic hyperplasia (BPH) is prescribed a new medication for his BPH. Within a week, he develops orthostatic hypotension and dizziness. Which of the following classes of medications was most likely prescribed?

The correct answer to the question "A 65-year-old male with a history of hypertension and benign prostatic hyperplasia (BPH) is prescribed a new medication for his BPH. Within a week, he develops orthostatic hypotension and dizziness. Which of the following classes of medications was most likely prescribed?" is Option C: Alpha-1 adrenergic antagonist (e.g., prazosin)..

The other options — A) 5-alpha reductase inhibitor (e.g., finasteride)., B) Muscarinic antagonist (e.g., oxybutynin)., D) Phosphodiesterase-5 inhibitor (e.g., sildenafil). — are incorrect for this USMLE Exam Prep question. As explained above: Alpha-1 adrenergic antagonists, used for BPH, can cause orthostatic hypotension due to their vasodilatory effects, especially in patients with existing hypertension or on antihypertensive medications.