Metyrosine
Pheochromocytoma
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Drug Status
Government Approvals
US(FDA)
WHO Essential Medicine
NO
Known Teratogen
No
Pharmaceutical Class
Catecholamine Synthesis Inhibitor
Controlled Drug Substance
No
Metyrosine
Summary
Metyrosine is used to treat pheochromocytoma, a condition where the body produces excessive catecholamines. It is also used for preoperative preparation and chronic treatment of malignant pheochromocytoma. However, it's not recommended for controlling essential hypertension.
Metyrosine works by inhibiting an enzyme called tyrosine hydroxylase, which is responsible for the first step in catecholamine biosynthesis. This reduces the production of catecholamines like norepinephrine and epinephrine, helping manage symptoms associated with their excess.
The usual starting dose for adults and children aged 12 and older is 250 mg taken orally four times a day. This dose can be increased up to a maximum of 4 grams per day. For children under 12, the dosage schedule is not established.
The most common side effect of Metyrosine is sedation. Other side effects include diarrhea, extrapyramidal signs, and anxiety or psychic disturbances. Serious adverse effects are rare but can include hematologic disorders and hypersensitivity reactions.
Metyrosine is contraindicated in individuals with hypersensitivity to it. It can cause sedation, so caution is advised when driving or operating machinery. Alcohol and CNS depressants can enhance its sedative effects. Adequate fluid intake is necessary to prevent crystalluria.
Indications and Purpose
How does Metyrosine work?
Metyrosine works by inhibiting the enzyme tyrosine hydroxylase, which is responsible for the first step in catecholamine biosynthesis. This inhibition reduces the production of catecholamines like norepinephrine and epinephrine, helping manage symptoms associated with their excess.
Is Metyrosine effective?
Metyrosine effectively reduces catecholamine biosynthesis in patients with pheochromocytoma, decreasing catecholamine levels by 35% to 80%. This reduction helps manage symptoms like hypertension, headaches, and tachycardia, proving its effectiveness in treating this condition.
What is Metyrosine?
Metyrosine is used to treat pheochromocytoma, a condition where the body produces excessive catecholamines like norepinephrine and epinephrine. It works by inhibiting tyrosine hydroxylase, reducing catecholamine biosynthesis and helping manage symptoms like hypertension and headaches.
Directions for Use
For how long do I take Metyrosine?
The typical duration of Metyrosine use varies depending on the condition being treated. For preoperative preparation, it is usually given for at least five to seven days. In chronic treatment, it can be used for several weeks to years, depending on the patient's response and medical advice.
How do I take Metyrosine?
Metyrosine can be taken with or without food. There are no specific food restrictions mentioned, but patients should maintain a liberal fluid intake to prevent crystalluria. Always follow your healthcare provider's instructions regarding dosage and administration.
How long does it take for Metyrosine to start working?
Metyrosine typically starts to show its maximum biochemical effect within two to three days of administration. The urinary concentration of catecholamines and their metabolites usually returns to pre-treatment levels within three to four days after discontinuation.
How should I store Metyrosine?
Store Metyrosine at room temperature, between 20° to 25°C (68° to 77°F). Keep it in a tight, child-resistant container to ensure safety and maintain its effectiveness.
What is the usual dose of Metyrosine?
The usual starting dose for adults and children aged 12 and older is 250 mg taken orally four times a day. This dose can be increased by 250 mg to 500 mg daily, up to a maximum of 4 grams per day, divided into multiple doses. For children under 12, the dosage schedule is not established.
Warnings and Precautions
Can I take Metyrosine with other prescription drugs?
Metyrosine can interact with phenothiazines or haloperidol, potentially enhancing their extrapyramidal effects. It also increases the sedative effects of alcohol and other CNS depressants. Patients should consult their healthcare provider about all medications they are taking.
Can Metyrosine be taken safely while breastfeeding?
It is not known whether Metyrosine is excreted in human milk. Due to the potential for adverse effects in nursing infants, caution should be exercised when administering Metyrosine to breastfeeding women. Consult a healthcare provider for personalized advice.
Can Metyrosine be taken safely while pregnant?
There is no strong evidence from human studies on the effects of Metyrosine during pregnancy. It should only be used if clearly needed, as its effects on fetal harm and reproduction capacity are unknown. Consult a healthcare provider for personalized advice.
Is it safe to drink alcohol while taking Metyrosine?
Drinking alcohol while taking Metyrosine can increase its sedative effects, leading to increased drowsiness or sedation. It is advisable to avoid alcohol consumption while on this medication to prevent these enhanced effects.
Is it safe to exercise while taking Metyrosine?
Metyrosine can cause sedation and fatigue, which may limit the ability to exercise. If you experience these side effects, it is advisable to avoid strenuous activities and consult a healthcare provider for guidance.
Is Metyrosine safe for the elderly?
For elderly patients, Metyrosine should be used cautiously, starting at the lower end of the dosing range. This is due to the higher likelihood of decreased liver, kidney, or heart function, and the presence of other health conditions or medications.
Who should avoid taking Metyrosine?
Metyrosine is contraindicated in individuals with hypersensitivity to the compound. It can cause sedation, so caution is advised when driving or operating machinery. Alcohol and CNS depressants can enhance its sedative effects. Adequate fluid intake is necessary to prevent crystalluria.
