A female client with a history of pheochromocytoma is admitted to the hospital in an acute hypertensive crisis. To reverse hypertensive crisis caused by pheochromocytoma. nurse Lyka expects to administer:

Phentolamine (Regitine).

Pheochromocytoma causes excessive production of epinephrine and norepinephrine. natural catecholamines that raise the blood pressure. Phentolamine. an alpha-adrenergic blocking agent given by I.V. bolus or drip. antagonizes the bodys response to circulating epinephrine and norepinephrine. reducing blood pressure quickly and effectively. Although methyldopa is an antihypertensive agent available in parenteral form. it isnt effective in treating hypertensive emergencies. Mannitol. a diuretic. isnt used to treat hypertensive emergencies. Felodipine. an antihypertensive agent. is available only in extended-release tablets and therefore doesnt reduce blood pressure quickly enough to correct hypertensive crisis.