Following the diagnosis of pheochromocytoma, medical management should be initiated with phenoxybenzamine (or alpha-1 adrenergic receptor antagonists, such as prazosin) to block alpha-adrenergic activity. Diuretics should not be used, and re-expansion of plasma volume may be accomplished by liberal salt or fluid intake. Low doses of a beta blocker such as propranolol are useful adjuncts to control blood pressure and cardiac tachyarrhythmias, but only after alpha blockade is established. Labetalol, an alpha- and beta-adrenergic blocker, has also been shown to be effective in the control of blood pressure and symptoms of pheochromocytoma. The use of combined alpha- and beta-adrenergic blockers or calcium antagonists can be continued on a long-term basis when the tumor is unresectable. For more refractory cases, or when severe and prolonged hypertension results from malignant disease, alpha-methyl-para-tyrosine is effective by inhibiting catecholamine synthesis.[1,2,3] This drug can decrease circulating catecholamines by 80% and alleviate many disease-related symptoms.[1,2,3,4]

References:

1. Manger WM, Gifford RW: Pheochromocytoma. New York: Springer-Verlag, 1977.
2. Young JB, Landsberg L: Catecholamines and the adrenal medulla: pheochromocytoma. In: Wilson JD, Foster DW, Kronenberg HM, et al., eds.: Williams Textbook of Endocrinology. 9th ed. Philadelphia, Pa: W.B. Saunders Company, 1998, pp 705-716.
3. Bravo EL, Gifford RW Jr: Current concepts. Pheochromocytoma: diagnosis, localization and management. N Engl J Med 311 (20): 1298-303, 1984.
4. Bravo EL: Evolving concepts in the pathophysiology, diagnosis, and treatment of pheochromocytoma. Endocr Rev 15 (3): 356-68, 1994.