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January 1, 1973

False-Positive Dopamine in Pheochromocytoma Treated With Tyrosine Derivative

Author Affiliations

Instituto N de Cardiologia Mexico

JAMA. 1973;223(1):80. doi:10.1001/jama.1973.03220010066029

To the Editor.—  Alpha-methyl-p-tyrosine is a drug under experimental use for the the treatment of pheochromocytoma, which also blocks the biosynthesis of catecholamine, inhibiting the tyrosine hydroxylase. Usually it gave a satisfactory control of arterial hypertension, together with a clear decrease in the excretion of norepinephrine and 4-hydroxy-3-methoxymandelic acid (vanillylmandelic acid [VMA]). Recently, we had the opportunity to study four patients with nonmalignant pheocromocytoma; three of them were excreting dopamine in higher levels than the normal rate during the control period. The tumors were localized; three extra-adrenally and one on the adrenal gland. After administration of alpha-methyl-p-tyrosine (500 to 2,000 mg/day), blood pressure was satisfactorily controlled and the excretion of norepinephrine and VMA markedly decreased. The dopamine, which was in levels above 1,000μg/24 hr increased in the patients with high dopamine excretion and reached values up to 8,000μg/24 hr in one of the patients after five