Racemetirosine is an orally active inhibitor of the enzyme tyrosine 3-monooxygenase, and consequently of the synthesis of catecholamine. At dosages of 600 to 3500mg daily, it is effective in controlling the hypertensive episodes and symptoms of catecholamine excess in phaeochromocytoma during preparation for surgery. Oral Racemetirosine is well absorbed and absorption appears constant in each individual over a wide dosage range. The drug is largely excreted via the kidneys, but extrarenal elimination has not been studied. Case reports on the clinical use of Racemetirosine in phaeochromocytoma indicate that the drug controls hypertension and symptoms of catecholamine excess in most patients during preparation for surgical removal of a tumor. In some cases, the addition of Racemetirosine to phenoxybenzamine plus propranolol has resulted in adequate control of symptoms previously unresponsive to the adrenergic blocking regimen. Drowsiness and sedation have been the most frequently reported side effects of Racemetirosine treatment.