All of the following drugs cause hypeensive crisis in patients with phaeochromocytoma, EXCEPT:
Phenoxybenzamine is used in the treatment of hypeensive crisis in pheochromocytoma, a catecholamine secreting tumor of cells derived from adrenal medulla. Prior to surgical of tumor, patients are treated with phenoxybenzamine, an alpha blocker to preclude the hypeensive crisis that can result from manipulation of the tissues. Beta blockers or other antihypeensives should not used without first blocking the alpha adrenoceptor mediated vasoconstriction. The goal of pre operative management is relaxation of constricted vasculature, expansion of reduced plasma volume and normalization of blood pressure. Beta blockers can be added to it if tachycardia persists, and CCBs and ACEIs can be added if BP is not controlled with phenoxybenzamine alone. Elevated levels of plasma and urinary catecholamines and the methylated metabolites, metanephrines, are the cornerstone for the diagnosis. T2-weighted MRI with gadolinium contrast is optimal for detecting pheochromocytomas and is somewhat better than CT for imaging extra-adrenal pheochromocytomas and paragangliomas. Ref: Pharmacology edited by Michelle A. Clark, page 88. Neumann H.P. (2012). Chapter 343. Pheochromocytoma. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds),Harrison's Principles of Internal Medicine, 18e. Primer on the Autonomic Nervous System edited by David Robeson, page 424.
Phenoxybenzamine
Propranolol
Saralasin
Captopril