No

Tyrosine Hydroxylase Inhibitor

Short-term management of pheochromocytoma before surgery, long-term management when surgery is contraindicated or when malignant

C

Hypertension of unknown etiology, known hypersensitivity to metyrosine

Maintain fluid volume during and after surgery; use with caution in patients with impaired renal or hepatic function

>10%:

Central nervous system: Drowsiness, extrapyramidal symptoms

Gastrointestinal: Diarrhea

1% to 10%:

Endocrine & metabolic: Galactorrhea, edema of the breasts

Gastrointestinal: Nausea, vomiting, xerostomia

Genitourinary: Impotence

Respiratory: Nasal congestion

<1%: Lower extremity edema, depression, hallucinations, disorientation, parkinsonism, urticaria, urinary problems, anemia, eosinophilia, hematuria, hyperstimulation after withdrawal

Signs of overdose include sedation, fatigue, tremor; reducing dose or discontinuation of therapy usually results in resolution of symptoms

Phenothiazines, haloperidol may potentiate EPS

Blocks the rate-limiting step in the biosynthetic pathway of catecholamines. It is a tyrosine hydroxylase inhibitor, blocking the conversion of tyrosine to dihydroxyphenylalanine. This inhibition results in decreased levels of endogenous catecholamines. Catecholamine biosynthesis is reduced by 35% to 80% in patients treated with metyrosine 1-4 g/day.

Half-life: 7.2 hours

Elimination: Following oral absorption, excreted primarily unchanged in urine

Children >12 years and Adults: Oral: Initial: 250 mg 4 times/day, increased by 250-500 mg/day up to 4 g/day; maintenance: 2-3 g/day in 4 divided doses; for preoperative preparation, administer optimum effective dosage for 5-7 days

Alcohol: Additive CNS effect, avoid use

Drowsiness and extrapyramidal reactions are common; may cause depression, hallucinations, or confusion

Concurrent use with antipsychotics may increase the risk of extrapyramidal symptoms

No information available to require special precautions

No effects or complications reported

Take plenty of fluids each day; may cause drowsiness, impair coordination and judgment; notify physician if drooling, tremors, speech difficulty, or diarrhea occurs; avoid alcohol and central nervous system depressants

Administer plenty of fluids each day; may cause drowsiness, impair coordination and judgment; notify physician if drooling, tremors, speech difficulty, or diarrhea occurs; avoid alcohol and central nervous system depressants

Capsule: 250 mg