Q. A 35-year-old male patient presents to your clinic with a chief complaint of headache, palpitations, and sweating episodes that have been occurring for the past two months. He reports that these symptoms occur randomly, but are often accompanied by a feeling of nervousness and increased heart rate. He has a past medical history of hypertension and reports that his blood pressure has been elevated for the past five years, despite being on antihypertensive medication. On physical examination, the patient's blood pressure is found to be elevated, with readings of 170/100 mm Hg. The patient is noted to be visibly uncomfortable, with signs of excessive sweating and a fast heart rate. A thorough review of symptoms is performed, and the patient reports a history of weight gain, fatigue, and frequent episodes of abdominal pain. Given the patient's symptoms and history, you order several diagnostic tests, including a 24-hour urine test for catecholamines and their metabolites, and an ultrasound of his abdomen. The results of the urine test reveal elevated levels of catecholamines, and the ultrasound shows a mass located in the adrenal gland, measuring approximately 3 cm in diameter (see image). Based on these findings, you make a diagnosis of pheochromocytoma. The patient is referred to a specialist for further evaluation and surgical management. While the patient awaits definitive treatment, which of the following medications is LEAST indicated?