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Pronunciation |
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(me
TYE roe
seen) |
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U.S. Brand
Names |
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Demser® |
|
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Generic
Available |
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No |
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Synonyms |
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AMPT; OGMT |
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Pharmacological Index |
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Tyrosine Hydroxylase Inhibitor |
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|
Use |
|
Short-term management of pheochromocytoma before surgery, long-term
management when surgery is contraindicated or when
malignant |
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Pregnancy Risk
Factor |
|
C |
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Contraindications |
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Hypertension of unknown etiology, known hypersensitivity to
metyrosine |
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Warnings/Precautions |
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Maintain fluid volume during and after surgery; use with caution in patients
with impaired renal or hepatic function |
|
|
Adverse
Reactions |
|
>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 |
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|
Overdosage/Toxicology |
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Signs of overdose include sedation, fatigue, tremor; reducing dose or
discontinuation of therapy usually results in resolution of
symptoms |
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|
Drug
Interactions |
|
Phenothiazines, haloperidol may potentiate EPS |
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|
Mechanism of
Action |
|
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. |
|
|
Pharmacodynamics/Kinetics |
|
Half-life: 7.2 hours
Elimination: Following oral absorption, excreted primarily unchanged in urine
|
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Usual Dosage |
|
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 |
|
|
Dietary
Considerations |
|
Alcohol: Additive CNS effect, avoid use |
|
|
Mental Health: Effects
on Mental Status |
|
Drowsiness and extrapyramidal reactions are common; may cause depression,
hallucinations, or confusion |
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|
Mental Health:
Effects on Psychiatric
Treatment |
|
Concurrent use with antipsychotics may increase the risk of extrapyramidal
symptoms |
|
|
Dental Health: Local
Anesthetic/Vasoconstrictor
Precautions |
|
No information available to require special precautions |
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Dental Health:
Effects on Dental Treatment |
|
No effects or complications reported |
|
|
Patient
Information |
|
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 |
|
|
Nursing
Implications |
|
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 |
|
|
Dosage Forms |
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Capsule: 250 mg |
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