A methylated tyrosine, a catecholamine synthesis antagonist with antihypertensive property. Metyrosine competitively inhibits tyrosine 3-monooxygenase, an enzyme that activates molecular oxygen to catalyze the hydroxylation of tyrosine to dihydroxyphenylalanine (Dopa), an intermediate to catecholamine (dopamine, norepinephrine, and epinephrine) production. This agent reduces the elevated levels of catecholamines associated with pheochromocytoma, thereby preventing hypertension.