Metyrosine
Mechanism :
It is tyrosine hydroxylase inhibitor, blocking the conversion of tyrosine to dihydroxyphenylalanine. This inhibition results in decreased levels of endogenous catecholamines.
Indication :
- Pheochromocytoma
- Note: Metyrosine is reserved for patients who cannot be treated with combined alpha- and beta-adrenergic blockade due to intolerance or cardiopulmonary reasons.
Contraindications :
Hypersensitivity to metyrosine or any component of the formulation.
Dosing :
≥12 years:
Initial: 250 mg PO 4 times/day, increased by 250 to 500 mg/day up to 4 g/day in 4 divided doses. Usual maintenance: 2 to 3 g/day in 4 divided dose.
For preoperative preparation, administer optimum effective dosage for 5 to 7 days.
Adverse Effect :
Extrapyramidal reaction, diarrhea, peripheral edema, anxiety, confusion, depression, disorientation, hallucination, headache, overstimulation (after withdrawal), Parkinson’s disease, sedation, urticarial, galactorrhea, breast swelling, crystalluria, dysuria, ejaculatory disorder, hematuria, impotence, anemia, eosinophilia, thrombocythemia, thrombocytopenia, hypersensitivity reaction.
Interaction :
Antipsychotic Agents: Metyrosine may enhance the adverse/toxic effect of Antipsychotic Agents.
CNS Depressants: May enhance the sedative effect of Metyrosine.
Selective Serotonin Reuptake Inhibitors: Metyrosine may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors.
Tricyclic Antidepressants: Metyrosine may enhance the adverse/toxic effect of Tricyclic Antidepressants.
Hepatic Dose :
No dose adjustments are recommended.