DEMSER- metyrosine capsule
Aton Pharma, Inc.
Rx only
DESCRIPTION
DEMSER 1 (Metyrosine) is (�)-?-methyl-L-tyrosine or (?-MPT). It has the following structural formula:
Chemical Structure
Metyrosine is a white, crystalline compound of molecular weight 195. It is very slightly soluble in water, acetone, and methanol, and insoluble in chloroform and benzene. It is soluble in acidic aqueous solutions. It is also soluble in alkaline aqueous solutions, but is subject to oxidative degradation under these conditions.
DEMSER is supplied as capsules, for oral administration. Each capsule contains 250 mg metyrosine. Inactive ingredients are colloidal silicon dioxide, gelatin, hydroxypropyl cellulose, magnesium stearate, titanium dioxide, and FD&C Blue 2.
1
Registered trademark of Valeant Pharmaceuticals International Inc. or its affiliates�Valeant Pharmaceuticals North America LLC
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CLINICAL PHARMACOLOGY
DEMSER inhibits tyrosine hydroxylase, which catalyzes the first transformation in catecholamine biosynthesis, i.e., the conversion of tyrosine to dihydroxyphenylalanine (DOPA). Because the first step is also the rate-limiting step, blockade of tyrosine hydroxylase activity results in decreased endogenous levels of catecholamines, usually measured as decreased urinary excretion of catecholamines and their metabolites.
In patients with pheochromocytoma, who produce excessive amounts of norepinephrine and epinephrine, administration of one to four grams of DEMSER per day has reduced catecholamine biosynthesis from about 35 to 80 percent as measured by the total excretion of catecholamines and their metabolites (metanephrine and vanillylmandelic acid). The maximum biochemical effect usually occurs within two to three days, and the urinary concentration of catecholamines and their metabolites usually returns to pretreatment levels within three to four days after DEMSER is discontinued. In some patients the total excretion of catecholamines and catecholamine metabolites may be lowered to normal or near normal levels (less than 10 mg/24 hours). In most patients the duration of treatment has been two to eight weeks, but several patients have received DEMSER for periods of one to 10 years. Most patients with pheochromocytoma treated with DEMSER experience decreased frequency and severity of hypertensive attacks with their associated headache, nausea, sweating, and tachycardia. In patients who respond, blood pressure decreases progressively during the first two days of therapy with DEMSER; after withdrawal, blood pressure usually increases gradually to pretreatment values within two to three days.
Metyrosine is well absorbed from the gastrointestinal tract. From 53 to 88 percent (mean 69 percent) was recovered in the urine as unchanged drug following maintenance oral doses of 600 to 4000 mg/24 hours in patients with pheochromocytoma or essential hypertension. Less than 1% of the dose was recovered as catechol metabolites. These metabolites are probably not present in sufficient amounts to contribute to the biochemical effects of metyrosine. The quantities excreted, however, are sufficient to interfere with accurate determination of urinary catecholamines determined by routine techniques.
Plasma half-life of metyrosine determined over an 8-hour period after single oral doses was 3-3.7 hours in three patients.
For further information, refer to: Sjoerdsma, A.; Engelman, K.; Waldman, T.A.; Cooperman, L.H.; Hammond, W.G.: Pheochromocytoma: Current concepts of diagnosis and treatment, Ann. Intern. Med. 65: 1302-1326, Dec. 1966.
INDICATIONS AND USAGE
DEMSER is indicated in the treatment of patients with pheochromocytoma for:
1. Preoperative preparation of patients for surgery
2. Management of patients when surgery is contraindicated
3. Chronic treatment of patients with malignant pheochromocytoma.
DEMSER is not recommended for the control of essential hypertension.
