Selective alpha blockers such as doxazosin are also commonly used to alpha block patients prior to pheochromocytoma resection. Selective alpha blockers are significantly less expensive and are associated with fewer side effects than phenoxybenzamine. Most retrospective studies comparing phenoxybenzamine with selective alpha blockers show no difference in intraoperative blood pressure fluctuations, morbidity, or mortality in pheochromocytoma resection. However, no prospective, randomized controlled trials comparing phenoxybenzamine to selective alpha blockers have been performed.