Introduction
Pheochromocytomas are catecholamine-releasing endocrine tumors of chromaffin cells. The secretion of catecholamines typically results in hypertension, either continuous or paroxysmal.
The latter represents a hypertensive crisis, and manifests as symptoms suggestive of seizure or anxiety attacks or hypertension that responds poorly to conventional therapy. Paroxysm or crisis occurs in over half of affected patients.1
Severe hemodynamic instability may occur during surgery to resect pheochromocytoma. DEMSER® is a therapy employed to help manage the hypertension of patients with pheochromocytoma in preparation for surgery, among other uses.
Important Safety Information
DEMSER® (Metyrosine) inhibits tyrosine hydroxylase which catalyses the first transformation in catecholamine biosynthesis, i.e., the conversion of tyrosine to dihydroxyphenylalanine (DOPA). When DEMSER is used preoperatively, adequate intravascular volume must be maintained intraoperatively (especially after tumor removal) and postoperatively to avoid hypotension and decreased perfusion of vital organs. Life threatening arrhythmias may occur during anesthesia and surgery. DEMSER does not eliminate the danger of hypertensive crises or arrhythmias during manipulation of the tumor. DEMSER may add to the sedative effects of alcohol and other CNS depressants. Metyrosine crystalluria has been observed in a few patients. Patients should be urged to maintain water intake sufficient to achieve a daily urine volume of 2000mL or more. If crystalluria persists, the dosage should be reduced or the drug discontinued. DEMSER should be used with caution in patients with impaired hepatic or renal function, and in patients receiving phenothiazines or haloperidol. Safety of use in pregnancy has not been established and caution should be exercised when DEMSER is administered to a nursing woman. Safety and efficacy in pediatric patients under the age of 12 has not been established. The most common adverse reaction to DEMSER is moderate to severe sedation, which has been observed in almost all patients. Extrapyramidal signs such as drooling, speech difficulty and tremor have been reported in 10 percent of the patients, occasionally accompanied by trismus and frank Parkinsonism. Anxiety and psychic disturbances may occur. Diarrhea occurs in about 10 percent of patients and may be severe. Other adverse reactions have been reported.
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Reference: 1. Landsberg L, Young JB. Pheochromocytoma. In: Kasper DL, Fauci AS, Longo DL, eds. Harrison's Principles of Internal Medicine. New York. 16th ed. McGraw-Hill. 2005; 2148-2150.
