Metyrosine

Description

DESCRIPTION Metyrosine is (–)-α-methyl- L -tyrosine or (α-MPT). It has the following structural formula: Metyrosine USP is a white to off-white, crystalline compound of molecular weight 195.22. 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. Metyrosine is supplied as capsules for oral administration. Each capsule contains 250 mg metyrosine, USP. Inactive ingredients are colloidal silicon dioxide, FD&C Blue # 2, gelatin, hydroxypropyl cellulose, low substituted hydroxypropyl cellulose, magnesium stearate and titanium dioxide. Each capsule is imprinted with black pharmaceutical ink which contains: black iron oxide, potassium hydroxide and shellac. Meets USP Dissolution Test 2. structural formula

What Is Metyrosine Used For?

INDICATIONS AND USAGE Metyrosine capsules are indicated in the treatment of patients with pheochromocytoma for: Preoperative preparation of patients for surgery Management of patients when surgery is contraindicated Chronic treatment of patients with malignant pheochromocytoma Metyrosine capsules are not recommended for the control of essential hypertension.

Dosage and Administration

DOSAGE AND ADMINISTRATION The recommended initial dosage of metyrosine capsules for adults and children 12 years of age and older is 250 mg orally four times daily. This may be increased by 250 mg to 500 mg every day to a maximum of 4 g/day in divided doses. When used for preoperative preparation, the optimally effective dosage of metyrosine capsules should be given for at least five to seven days. Optimally effective dosages of metyrosine usually are between 2 and 3 g/day, and the dose should be titrated by monitoring clinical symptoms and catecholamine excretion. In patients who are hypertensive, dosage should be titrated to achieve normalization of blood pressure and control of clinical symptoms. In patients who are usually normotensive, dosage should be titrated to the amount that will reduce urinary metanephrines and/or vanillylmandelic acid by 50% or more. If patients are not adequately controlled by the use of metyrosine, an alpha-adrenergic blocking agent (phenoxybenzamine) should be added. Use of metyrosine in children under 12 years of age has been limited and a dosage schedule for this age group cannot be given.

Side Effects (Adverse Reactions)

ADVERSE REACTIONS Central Nervous System Sedation: The most common adverse reaction to metyrosine is moderate to severe sedation, which has been observed in almost all patients. It occurs at both low and high dosages. Sedative effects begin within the first 24 hours of therapy, are maximal after two to three days, and tend to wane during the next few days. Sedation usually is not obvious after one week unless the dosage is increased, but at dosages greater than 2,000 mg/day some degree of sedation or fatigue may persist. In most patients who experience sedation, temporary changes in sleep pattern occur following withdrawal of the drug. Changes consist of insomnia that may last for two or three days and feelings of increased alertness and ambition. Even patients who do not experience sedation while on metyrosine may report symptoms of psychic stimulation when the drug is discontinued. Extrapyramidal Signs: Extrapyramidal signs such as drooling, speech difficulty, and tremor have been reported in approximately 10% of patients. These occasionally have been accompanied by trismus and frank parkinsonism. Anxiety and Psychic Disturbances: Anxiety and psychic disturbances such as depression, hallucinations, disorientation, and confusion may occur. These effects seem to be dose-dependent and may disappear with reduction of dosage. Diarrhea Diarrhea occurs in about 10% of patients and may be severe. Anti-diarrheal agents may be required if continuation of metyrosine is necessary. Miscellaneous Infrequently, slight swelling of the breast, galactorrhea, nasal stuffiness, decreased salivation, dry mouth, headache, nausea, vomiting, abdominal pain, and impotence or failure of ejaculation may occur. Crystalluria (see PRECAUTIONS ) and transient dysuria and hematuria have been observed in a few patients. Hematologic disorders (including eosinophilia, anemia, thrombocytopenia, and thrombocytosis), increased SGOT levels, peripheral edema, and hypersensitivity reactions such as urticaria and pharyngeal edema have been reported rarely. To report SUSPECTED ADVERSE REACTIONS, contact Cerovene, Inc. at 1-833-304-9569 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Drug Interactions

Drug Interactions Caution should be observed in administering metyrosine to patients receiving phenothiazines or haloperidol because the extrapyramidal effects of these drugs can be expected to be potentiated by inhibition of catecholamine synthesis. Concurrent use of metyrosine with alcohol or other CNS depressants can increase their sedative effects. (See WARNINGS and PRECAUTIONS , Information for Patients .)

Contraindications

CONTRAINDICATIONS Metyrosine capsules are contraindicated in persons known to be hypersensitive to this compound.

Pregnancy and Breastfeeding

Pregnancy Pregnancy: Animal reproduction studies have not been conducted with metyrosine. It is also not known whether metyrosine can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Metyrosine should be given to a pregnant woman only if clearly needed.

Nursing Mothers It is not known whether metyrosine is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when metyrosine is administered to a nursing woman.

Overdosage

OVERDOSAGE Signs of metyrosine overdosage include those central nervous system effects observed in some patients even at low dosages. At doses exceeding 2,000 mg/day, some degree of sedation or feeling of fatigue may persist. Doses of 2,000 to 4,000 mg/day can result in anxiety or agitated depression, neuromuscular effects (including fine tremor of the hands, gross tremor of the trunk, tightening of the jaw with trismus), diarrhea, and decreased salivation with dry mouth. Reduction of drug dose or cessation of treatment results in the disappearance of these symptoms. The acute toxicity of metyrosine was 442 mg/kg and 752 mg/kg in the female mouse and rat, respectively.

How Supplied

HOW SUPPLIED Metyrosine Capsules USP, 250 mg are light blue opaque body with a print “315” /blue opaque cap with a print “C” filled with white to off-white powder. They are supplied as follows: NDC 75907-166-01 bottles of 100 NDC 75907-166-30 bottles of 30 Storage: Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Dispense in a well-closed container. Manufactured by: Cerovene Inc. Valley Cottage, NY 10989 Manufactured For: Dr. Reddy's Laboratories Inc. Princeton, NJ 08540 USA Issued: 03/2024 CEROVENE